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Excitatory and inhibitory 5-hydroxytryptamine (5HT) receptors expressed in the isolated porcine uterine muscles
5-Hydroxytryptamine (5-HT) receptors mediating excitatory and inhibitory actions of 5-HT on contractility of uterine strips from non-pregnant pigs were characterized. Expression of 5-HT2A and 5-HT7 receptors was examined by molecular biological study. 5-HT-containing cells were observed immunohistochemically. In the spontaneously contracting uterine circular muscle layers, 5-HT caused inhibition of contractile activity. SB269970 (5-HT7 receptor antagonist, 10ĀnM) shifted the concentration-inhibition curve
Tatsuro Nakamura; Takio Kitazawa; Jinshan Cao; Takuya Iwamoto; Hiroki Teraoka; Koichi Kadota; Tetsuro Taneike
Clozapine downregulates 5-hydroxytryptamine 6 (5HT 6) and upregulates 5HT 7 receptors in HeLa cells
Clozapine is an atypical antipsychotic with high affinity for several serotonin receptors. This drug causes paradoxical downregulation of 5-hydroxytryptamine2A (5-HT)2A receptors, but its modulation of other serotonin receptors has not been studied. We examined the effects of clozapine and several other drugs on the regulation of rat 5-HT6 and 5-HT7 receptors individually expressed in transfected HeLa cells. Both 5-HT6 and
Natalia L Zhukovskaya; John F Neumaier
5-Hydroxytryptamine and human small intestinal motility: effect of inhibiting 5-hydroxytryptamine reuptake.
Parenteral 5-hydroxytryptamine stimulates small intestinal motility, but the effect of continuous stimulation with 5-hydroxytryptamine on the human migrating motor complex is unknown. Using a selective 5-hydroxytryptamine reuptake inhibitor, paroxetine, this study investigated the effect of indirect 5-hydroxytryptamine agonism on fasting small intestinal motility and transit. Eight healthy subjects were studied while receiving paroxetine 30 mg daily for five days and while receiving no treatment, in random order. Ambulant small intestinal motility was recorded from five sensors positioned from the duodenojejunal flexure to the ileum for 16-18 hours. Paroxetine reduced the migrating motor complex periodicity mean (SEM) from 81 (6) min to 67 (4) min (p < 0.05), and increased the propagation velocity of phase III from 3.1 to 4.7 cm/min in the proximal jejunum (p < 0.01), and from 1.6 to 3.4 cm/min distally (p < 0.001). Orocaecal transit time measured by lactulose hydrogen breath test was reduced by paroxetine from 70 (9) min to 48 (7) min (p < 0.05). These data suggest that 5-hydroxytryptamine participates in the control of migrating motor complexes in humans, and that selective 5-hydroxytryptamine reuptake inhibitors have a prokinetic action in the human small intestine.
Gorard, D A; Libby, G W; Farthing, M J
5-HT1 agonists reduce 5-hydroxytryptamine release in rat hippocampus in vivo as determined by brain microdialysis.
1. An intracerebral perfusion method, brain microdialysis, was used to assess changes of 5-hydroxytryptamine (5-HT) release in the ventral hippocampus of the chloral hydrate-anaesthetized rat in response to systemic administration of a variety of 5-HT1 receptor agonists. 2. A stable output of reliably detectable endogenous 5-HT was measured in dialysates collected from ventral hippocampus with the 5-HT reuptake inhibitor, citalopram, present in the perfusion medium. 3. Under these conditions the putative 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) caused a dose-dependent (5-250 micrograms kg-1, s.c.) reduction of 5-HT in hippocampal dialysates. 4. Similarly, the putative 5-HT1A agonists gepirone (5 mg kg-1, s.c.), ipsapirone (5 mg kg-1, s.c.) and buspirone (5 mg kg-1, s.c.) markedly reduced levels of 5-HT in hippocampal perfusates whereas their common metabolite 1-(2-pyrimidinyl) piperazine (5 mg kg-1, s.c.), which does not bind to central 5-HT1A recognition sites, had no effect. 5. 5-Methoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole (RU 24969), a drug with reported high affinity for brain 5-HT1B binding sites, also produced a dose-dependent (0.25-5 mg kg-1, s.c.) decrease of hippocampal 5-HT output. 6. These data are direct biochemical evidence that systemically administered putative 5-HT1A and 5-HT1B agonists markedly inhibit 5-HT release in rat ventral hippocampus in vivo.
Sharp, T.; Bramwell, S. R.; Grahame-Smith, D. G.
Stimulation of Growth Hormone Release by 5Hydroxytryptamine (5HT) in Cultured Rat Anterior Pituitary Cell Aggregates: Evidence for Mediation by 5HT2B, 5HT7, 5HT1B, and Ketanserin-Sensitive Receptors
5-Hydroxytryptamine (5-HT) promotes the release of GH by a hypothalamic site of action. The present study explores a pu- tative pituitary action in a perifused rat anterior pituitary aggregate cell culture system. In aggregates cultured with 1 nMestradiolforexpressionofthe5-HT4,-5,and-6receptor(R), 5-HT promptly stimulated GH secretion with a dose depen- dency between 1 and 10 nM. The effect of 5-HT was partially blocked
A. Papageorgiou; C. Denef
Pharmacological characterization of RP 62203, a novel 5-hydroxytryptamine 5-HT2 receptor antagonist
1 RP 62203 (2-[3-(4-(4-fluorophenyl)-piperazinyl)propyl]naphto[1,8-cd]isothiazole-1, 1-dioxide) is a novel naphtosultam derivative which shows very high affinity for 5-HT2 receptors in the rat cerebral cortex (Ki = 50.0 pM). 2 RP 62203 is relatively selective for this sub-type of 5-hydroxytryptamine (5-HT) receptor, having lower affinity for the 5-HT1A receptor and very low affinity for the 5-HT3 receptor. RP 62203 displayed low to moderate affinity for ?1-adrenoceptors, dopamine D2 receptors and histamine H1 receptors. 3 In vivo binding experiments demonstrated that oral administration of low doses of RP 62203 led to a long-lasting (>6h) occupation of cortical 5-HT2 receptors (ID50 = 0.39 mg kg-1). 4 In cortical slices from the neonatal rat, RP 62203 potently inhibited inositol phosphate formation evoked by 5-HT, with an IC50 of 7.76 nM. 5 The activity of neurones in the raphķ and their responses to microiontophoretically applied 5-HT were studied with extracellular recording electrodes in the anaesthetized rat. RP 62203 potently and dose-dependently blocked excitations evoked by 5-HT when administered at doses of 0.5¢4.0 mg kg-1, i.p. In contrast, neither 5-HT-evoked depressions nor glutamate-evoked excitations of raphķ neuronal firing were blocked by RP 62203 at doses as high as 8.0 mg kg-1, i.p. 6 Head twitches induced by 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) could be abolished by low doses of RP 62203 in mice (ED50 = 0.44 mg kg-1, p.o.) and in rats (ED50 = 1.54 p.o.). Similar results were obtained with mescaline and 5-hydroxytryptophan (5-HTP). 7 The potency of RP 62203 was compared with that of three other 5-HT2 receptor antagonists, ritanserin, ICI 169,369 and ICI 170,809. In all models, RP 62203 showed similar activity to ritanserin, whilst either ICI 169,369 or ICI 170,809 was several fold less active. 8 It is concluded that RP 62203 is a potent and selective antagonist at 5-HT2 receptors in the rodent central nervous system.
Doble, A.; Girdlestone, D.; Piot, O.; Allam, D.; Betschart, J.; Boireau, A.; Dupuy, A.; Gueremy, C.; Menager, J.; Zundel, J.L.; Blanchard, J.C.
5Hydroxytryptamine 7 (5HT 7) receptor immunoreactivity-positive æstigmoid bodyÆ-like structure in developing rat brains
We examined the expression of 5-hydroxytryptamine7 (5-HT7) receptor protein in developing and adult rats with immunohistochemical technique. In adult male rats, 5-HT7 receptor immunoreactivity was detected in the septum, striatum, indusium griseum, tenia tecta, thalamus, hippocampus and hypothalamus in the forebrain as well as the pons and cerebellum. In brains of 1, 7, 15 and 21 days old male rats
Katsumasa T Muneoka; Morikuni Takigawa
5-hydroxytryptamine (5-HT) reduces total peripheral resistance during chronic infusion: direct arterial mesenteric relaxation is not involved
Serotonin (5-hydroxytryptamine; 5-HT) delivered over 1?week results in a sustained fall in blood pressure in the sham and deoxycorticosterone acetate (DOCA)-salt rat. We hypothesized 5-HT lowers blood pressure through direct receptor-mediated vascular relaxation. In vivo, 5-HT reduced mean arterial pressure (MAP), increased heart rate, stroke volume, cardiac index, and reduced total peripheral resistance during a 1?week infusion of 5-HT (25 Ąg/kg/min) in the normotensive Sprague Dawley rat. The mesenteric vasculature was chosen as an ideal candidate for the site of 5-HT receptor mediated vascular relaxation given the high percentage of cardiac output the site receives. Real-time RT-PCR demonstrated that mRNA transcripts for the 5-HT2B, 5-HT1B, and 5-HT7 receptors are present in sham and DOCA-salt superior mesenteric arteries. Immunohistochemistry and Western blot validated the presence of the 5-HT2B, 5- HT1B and 5-HT7 receptor protein in sham and DOCA-salt superior mesenteric artery. Isometric contractile force was measured in endothelium-intact superior mesenteric artery and mesenteric resistance arteries in which the contractile 5- HT2A receptor was antagonized. Maximum concentrations of BW-723C86 (5- HT2B agonist), CP 93129 (5-HT1B agonist) or LP-44 (5-HT7 agonist) did not relax the superior mesenteric artery from DOCA-salt rats vs. vehicle. Additionally, 5-HT (10¢9?M to 10¢5?M) did not cause relaxation in either contracted mesenteric resistance arteries or superior mesenteric arteries from normotensive Sprague- Dawley rats. Thus, although 5-HT receptors known to mediate vascular relaxation are present in the superior mesenteric artery, they are not functional, and are therefore not likely involved in a 5-HT-induced fall in total peripheral resistance and MAP.
5-hydroxytryptamine (5-HT) reduces total peripheral resistance during chronic infusion: direct arterial mesenteric relaxation is not involved.
Serotonin (5-hydroxytryptamine; 5-HT) delivered over 1 week results in a sustained fall in blood pressure in the sham and deoxycorticosterone acetate (DOCA)-salt rat. We hypothesized 5-HT lowers blood pressure through direct receptor-mediated vascular relaxation. In vivo, 5-HT reduced mean arterial pressure (MAP), increased heart rate, stroke volume, cardiac index, and reduced total peripheral resistance during a 1 week infusion of 5-HT (25 Ąg/kg/min) in the normotensive Sprague Dawley rat. The mesenteric vasculature was chosen as an ideal candidate for the site of 5-HT receptor mediated vascular relaxation given the high percentage of cardiac output the site receives. Real-time RT-PCR demonstrated that mRNA transcripts for the 5-HT2B, 5-HT1B, and 5-HT7 receptors are present in sham and DOCA-salt superior mesenteric arteries. Immunohistochemistry and Western blot validated the presence of the 5-HT2B, 5- HT1B and 5-HT7 receptor protein in sham and DOCA-salt superior mesenteric artery. Isometric contractile force was measured in endothelium-intact superior mesenteric artery and mesenteric resistance arteries in which the contractile 5- HT2A receptor was antagonized. Maximum concentrations of BW-723C86 (5- HT2B agonist), CP 93129 (5-HT1B agonist) or LP-44 (5-HT7 agonist) did not relax the superior mesenteric artery from DOCA-salt rats vs. vehicle. Additionally, 5-HT (10-9 M to 10-5 M) did not cause relaxation in either contracted mesenteric resistance arteries or superior mesenteric arteries from normotensive Sprague- Dawley rats. Thus, although 5-HT receptors known to mediate vascular relaxation are present in the superior mesenteric artery, they are not functional, and are therefore not likely involved in a 5-HT-induced fall in total peripheral resistance and MAP. PMID:22559843
Davis, Robert Patrick; Pattison, Jill; Thompson, Janice M; Tiniakov, Ruslan; Scrogin, Karie E; Watts, Stephanie W
Predictive In Silico Studies of Human 5-hydroxytryptamine Receptor Subtype 2B (5-HT2B) and Valvular Heart Disease
Serotonin (5-HT) receptors are neuromodulator neurotransmitter receptors which when activated generate a signal transduction pathway within cells resulting in cell-cell communication. 5-hydroxytryptamine (serotonin) receptor 2B (5-HT2B) is a subtype of the seven members of 5-hydroxytrytamine (5-HT) family of receptors which is the largest member of the super family of 7-transmembrane G-protein coupled receptors (GPCRs). Not only do 5-HT receptors play physiological roles in the cardiovascular system, gastrointestinal and endocrine function and the central nervous, but they also play a role in behavioral functions. In particular 5-HT2B receptor is wide spread with regards to its distribution throughout bodily tissues and is expressed at high levels in the lungs, peripheral tissues, liver, kidney and prostate just to name a few. Hence 5-HT2B participates in multiple biological functions including CNS regulation, regulation of gastrointestinal motality, cardiovascular regulation and 5-HT transport system regulation. While 5-HT2B is a viable drug target and has therapeutic indications for treating obesity, psychotherapy, ParkinsonÆs disease etc. there is a growing concern regarding adverse drug reactions, specifically valvulopathy associated with 5-HT2B agonists. Due to the sequence homology experienced by 5-HT2 subtypes there is also a concern regarding the off target effects of 5-HT2A and 5-HT2C agonists. The concept of subtype selectivity is of paramount importance and can be tackled with the aid of in silico studies, specifically cheminformatics, to develop models to predict valvulopathy associated toxicity of drug candidates prior to clinical trials. This review has highlighted three in silico approaches thus far that have been successful in either predicting 5-HT2B toxicity of molecules or identifying important interactions between 5-HT2B and drug molecules that bring about valvulopathy related toxicities.
Reid, Terry-Elinor; Kumar, Krishna
Role of 5-hydroxytryptamine 1B (5-HT1B) receptors in the regulation of ethanol intake in rodents
Evidence indicates that the serotonergic system is important in mediating dependence on and craving for alcohol. Among serotonin receptors, 5-hydroxytryptamine 1B (5-HT1B) receptors have been associated with drug abuse including alcohol. In this review, the neurocircuitry involving 5-HT1B receptors in central reward brain regions related to alcohol intake are discussed in detail. Emphasis has been placed on the pharmacological manipulations of 5-HT1B receptor-mediated alcohol intake. Furthermore, 5-HT1B auto- and hetero-receptors regulate alcohol intake through the regulatory mechanism involving release of 5-HT, gamma-aminobutyric acid (GABA), dopamine, and glutamate is evaluated. Thus, interactions between 5-HT1B receptors and these neurotransmitter systems are suggested to modulate alcohol-drinking behavior. This review on the role of 5-HT1B receptors in neurotransmitter release and consequent alcohol intake provides important information about the potential therapeutic role of 5-HT1B receptors for the treatment of alcohol dependence.
Sari, Youssef
The study of 5-hydroxytryptamine (5-HT) system has benefited from the identification, classification and cloning of multiple 5-HT receptors (5-HT1 to 5-HT7). Growing evidence suggests that 5-HT is important in learning and memory and all its receptors might be implicated in this. Actually, 5-HT pathways, 5-HT reuptake site\\/transporter complex and 5-HT receptors show regional distribution in brain areas implicated in learning
A. Meneses
Further characterization of 5-hydroxytryptamine receptors (putative 5-HT2B) in rat stomach fundus longitudinal muscle.
1. The present study was undertaken to isolate and characterize pharmacologically homogeneous populations of 5-hydroxytryptamine (5-HT) receptors from a possible mixed receptor population mediating concentration of the longitudinal muscle of rat stomach fundus. Our aim was to extend the pharmacological characterization of the 5-HT2B receptor which is reported to be expressed in this preparation. 2. To minimize spontaneous activity and any influence of circular muscle on the contractile response, narrow (1-1.5 x 20 mm) segments of mucosa-denuded longitudinal muscle were used. Under these conditions, blockade of monoamine oxidase with pargyline (100 microM for 15 min) caused a leftward displacement of concentration-effect curves for both 5-methoxytryptamine (5-MeO-T) and tryptamine. Neither pargyline nor a number of uptake inhibitors affected responses to 5-HT. 3. In pargyline pretreated preparations, the order of potency of a number of tryptamine analogues was as follows: 5-MeO-T > or = alpha-Me-5-HT > or = 5-HT > 5-carboxamidotryptamine (5-CT) > tryptamine > 2-Me-5-HT. In addition several ligands known to act as agonists at either 5-HT2A or 5-HT2C receptors including 1-m-chlorophenylpiperazine (m-CPP), Ru 24969, MK 212 and SCH 23390 were also agonists in rat fundus whilst sumatriptan, renzapride and 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) were very weak or inactive. With the exception of 2-Me-5-HT and m-CPP, most agonists produced monophasic concentration-effect curves consistent with an interaction at a single site.(ABSTRACT TRUNCATED AT 250 WORDS)
Baxter, G. S.; Murphy, O. E.; Blackburn, T. P.
RIC-3 Exclusively Enhances the Surface Expression of Human Homomeric 5-Hydroxytryptamine Type 3A (5-HT3A) Receptors Despite Direct Interactions with 5-HT3A, -C, -D, and -E Subunits*
Although five 5-hydroxytryptamine type 3 (5-HT3) subunits (A¢E) have been cloned, knowledge on the regulation of their assembly is limited. RIC-3 has been identified as a chaperone specific for the pentameric ligand-gated nicotinic acetylcholine and 5-HT3 receptors. Therefore, we examined the impact of RIC-3 on differently composed 5-HT3 receptors with the focus on 5-HT3C, -D, and -E subunits. The influence of RIC-3 on these receptor subtypes is supported by the presence of RIC3 mRNA in tissues expressing at least one of the subunits 5-HT3C, -D, and -E. Furthermore, immunocytochemical studies on transfected mammalian cells revealed co-localization in the endoplasmic reticulum and direct interaction of RIC-3 with 5-HT3A, -C, -D, and -E. Functional and pharmacological characterization was performed using HEK293 cells expressing 5-HT3A or 5-HT3A + 5-HT3B (or -C, -D, or -E) in the presence or absence of RIC-3. Ca2+ influx analyses revealed that RIC-3 does not influence the 5-HT concentration-response relationship on 5-HT3A receptors but leads to differential increases of 5-HT-induced maximum response (Emax) on cells expressing different subunits. Increases of Emax were due to analogously enhanced Bmax values for binding of the 5-HT3 receptor antagonist [3H]GR65630. The observed enhanced cell surface expression of the tested 5-HT3 subunit combinations correlated with the increased surface expression of 5-HT3A as determined by flow cytometry. In conclusion, we showed that RIC-3 can interact with 5-HT3A, -C, -D, and -E subunits and predominantly enhances the surface expression of homomeric 5-HT3A receptors in HEK293 cells. These data implicate a possible role of RIC-3 in determining 5-HT3 receptor composition in vivo.
Walstab, Jutta; Hammer, Christian; Lasitschka, Felix; Moller, Dorothee; Connolly, Christopher N.; Rappold, Gudrun; Bruss, Michael; Bonisch, Heinz; Niesler, Beate
Function and distribution of three rat 5-hydroxytryptamine 7 (5HT 7) receptor isoforms produced by alternative splicing
Serotonin (5-HT7) receptor pre-mRNA is alternatively spliced in rat tissue to produce three isoforms, 5-HT(7a), 5-HT(7b) and 5-HT(7c), which differ in the amino acid sequences of their carboxyl terminal tails. Substantial species differences in structure and expression patterns exist for 5-HT7 isoforms. We have now compared some of the functional characteristics and level of expression for the three rat 5-HT7
Doris E. A. Heidmann; Patricia Szot; Ruth Kohen; Mark W. Hamblin
SB-649915, a novel, potent 5-HT1A and 5-HT1B autoreceptor antagonist and 5-HT re-uptake inhibitor in native tissue.
An increase in brain 5-HT levels is thought to be the key mechanism of action which results in an antidepressant response. It has been proven that selective serotonin re-uptake inhibitors are effective antidepressants but the delay to therapeutic onset of these agents is thought to be due to the time required for 5-HT1A, and possibly 5-HT1B, autoreceptor desensitisation. Therefore an agent incorporating 5-HT re-uptake inhibition coupled with 5-HT1A and/or 5-HT1B autoreceptor antagonism may provide a fast acting clinical agent. The current studies describe the in vitro profile of SB-649915 (6-[(1-{2-[(2-methylquinolin-5-yl)oxy]ethyl}piperidin-4-yl)methyl]-2H-1,4-benzoxazin-3(4H)-one), a novel compound which has high affinity for human recombinant 5-HT1A, 5-HT1B and 5-HT1D receptors (pKi values of 8.6, 8.0, 8.8, respectively) and the human recombinant 5-HT transporter (pKi value of 9.3). SB-649915 also displays high affinity for rat, guinea pig, mouse and marmoset native tissue 5-HT1A, 5-HT1B and 5-HT1D receptors and rat native tissue 5-HT transporters (pKi values>or=7.5). In functional [35S]GTPgammaS binding studies, SB-649915 (up to 1 microM) does not display intrinsic activity in HEK293 cells expressing human recombinant 5-HT1A receptors but acts as a partial agonist at human recombinant 5-HT1B and 5-HT1D receptors with intrinsic activity values of 0.3 and 0.7, respectively, as compared to the full agonist 5-HT. From Schild analysis, SB-649915 caused a concentration-dependent, rightward shift of 5-HT-induced stimulation of basal [35S]GTPgammaS binding in cells expressing human recombinant 5-HT1A or 5-HT1B receptors to yield pA2 values of 9.0 and 7.9, respectively. In electrophysiological studies in rat dorsal raphe nucleus, SB-649915 did not affect the cell firing rate up to 1 microM but attenuated (+)8-hydroxy-2-(di-n-propylamino) tetralin-induced inhibition of cell firing with an apparent pKb value of 9.5. SB-649915 (1 microM) significantly attenuated exogenous 5-HT-induced inhibition of electrically-stimulated [3H]5-HT release from guinea pig cortex. In studies designed to enhance endogenous 5-HT levels, and therefore increase tone at 5-HT1B autoreceptors, SB-649915 significantly potentiated [3H]5-HT release at 100 and 1000 nM. In LLCPK cells expressing human recombinant 5-HT transporters and in rat cortical synaptosomes, SB-649915 inhibited [3H]5-HT re-uptake with pIC50 values of 7.9 and 9.7, respectively. In summary, SB-649915 is a novel, potent 5-HT1A/1B autoreceptor antagonist and 5-HT re-uptake inhibitor in native tissue systems and represents a novel mechanism that could offer fast acting antidepressant action. PMID:16571351
Scott, Claire; Soffin, Ellen M; Hill, Matthew; Atkinson, Peter J; Langmead, Christopher J; Wren, Paul B; Faedo, Stefania; Gordon, Laurie J; Price, Gary W; Bromidge, Steve; Johnson, Christopher N; Hagan, James J; Watson, Jeannette
Assessment of binding affinity to 5-hydroxytryptamine 2A (5-HT2A) receptor and inverse agonist activity of naftidrofuryl: comparison with those of sarpogrelate.
Naftidrofuryl is a peripheral vasodilator that has been clinically used in the treatment of intermittent claudication and dementia. It has 5-hydroxytryptamine 2 (5-HT(2)) antiserotonergic activity and selectively binds with the 5-HT(2) receptor. The purpose of the present study is to assess the binding affinity and functional potency of naftidrofuryl to the 5-HT(2A) receptor, to find out the inverse agonist activity of this compound at a constitutively active mutant of 5-HT(2A) receptor, and finally to compare the findings with those of sarpogrelate. The investigation showed that the binding affinity (pK(i)) of naftidrofuryl was decreased 25- or 50-fold compared to sarpogrelate in the wild-type 5-HT(2A) receptor or Cys322Lys mutant receptor, respectively. Moreover, the functional potency (pK(b)) of naftidrofuryl was much lower compared to sarpogrelate at the 5-HT(2A) receptor. In addition, inverse agonist activity of naftidrofuryl was lower compared with sarpogrelate at the constitutively active mutant receptor. Thus, the data of the present study would be very important for the clarification of interaction sites of naftidrofuryl to 5-HT(2A) receptors and also may help to understand the mechanism of inverse agonist activity at the constitutively active mutant receptor. PMID:19672037
Aly, Saida Abdel Regal; Hossain, Murad; Bhuiyan, Mohiuddin Ahmed; Nakamura, Takashi; Nagatomo, Takafumi
5-Hydroxytryptamine potentiates neurogenic contractions of rat isolated urinary bladder through both 5-HT(7) and 5-HT(2C) receptors.
Serotonin (5-HT) enhances the neurogenic contractile response induced by electrical field stimulation (EFS) in the rat isolated urinary bladder. The aim of this study was to functionally characterize the receptors involved in this effect by using a range of 5-HT receptor subtype selective agonists and antagonists. 5-HT produced a concentration-dependent potentiation of contractile responses to EFS with a pEC(50) value of 6.86▒0.24. SB-269970 (0.01, 0.1 and 1?M), a selective 5-HT(7) receptor antagonist, caused a concentration-dependent rightward shift of the 5-HT-induced response. The pA(2) value was 8.16 with a slope of 0.46▒0.08. Neither ketanserine nor SB-204741, 5-HT(2A) and 5-HT(2B) receptors antagonists, respectively, affected the concentration-response curve to 5-HT. However, 5-HT response was antagonized by the selective 5-HT(2C) receptor antagonist SB-242084 (0.1 and 1?M). In the presence of 1?M of both antagonists SB-269970 and SB-242084, 5-HT response was almost fully inhibited. 5-CT, a 5-HT(7) receptor agonist, induced a biphasic concentration-dependent potentiation of neurogenic contractions. SB-269970 concentration-dependently antagonized the first phase of 5-CT response with a pA(2) value of 8.77 and a slope not significantly different from unity (0.91▒0.11) that suggests a competitive antagonism. WAY-161503, a 5-HT(2C) receptor agonist (0.01-10?M), induced a concentration-dependent potentiation of contractile response to EFS while DOI (a selective 5-HT(2A) agonist) had no effect. SB-242084 (0.1 and 1?M) antagonized the effect of WAY-161503 in a concentration-dependent manner. The current results demonstrate that 5-HT potentiates neurogenic contractions of rat isolated detrusor muscle through both 5-HT(7) and 5-HT(2c) receptors. PMID:20969855
Rekik, MoĶz; Lluel, Philippe; Palea, Stefano
Involvement of 5-hydroxytryptamine 5-HT? serotonergic receptors in the acquisition and reinstatement of the conditioned place preference induced by MDMA.
Some MDMA (3,4-methylenedioxymethamphetamine) users develop dependence as a result of chronic consumption. The present study evaluated the role of 5-hydroxytryptamine 5-HT? receptors in the acquisition, expression and reinstatement of the conditioned place preference (CPP) induced by MDMA. Adolescent male mice were conditioned with 10 mg/kg of MDMA and then treated with 1 or 3mg/kg of the 5-hydroxytryptamine 5-HT? antagonist MDL72222 during acquisition of conditioning (experiment 1), before expression of CPP in a post-conditioning test (experiment 2) or before a reinstatement test (experiment 3). MDL72222 was devoid of motivational effects but blocked acquisition of the MDMA-induced CPP. Moreover, following extinction, the low dose of MDL72222 blocked reinstatement of the CPP induced by priming with MDMA. Acute MDMA reduced levels of dihydroxypheylacetic acid (DOPAC) in the striatum and levels of acid 5-hydroxyindoleacetic (5-HIAA) in the cortex. Acute MDMA+MDL72222 also reduced striatal DOPAC. The repeated co-administration of MDMA plus MDL72222 (on PND 32-34-36-38) increased dopamine and decreased DOPAC in the striatum, and increased cortical serotonin and enhanced transporters of dopamine and serotonin. The acute administration (on PND ▒55) of MDMA or MDL72222 increased levels of dopamine and reduced those of DOPAC in the striatum and co-administration of MDMA plus MDL72222 increased striatal serotonin. Our results confirm that 5-hydroxytryptamine 5-HT? receptors are involved in the acquisition of conditioned rewarding effects of MDMA and demonstrate that these receptors are also involved in reinstatement after extinction. PMID:23792143
Roger-Sßnchez, Concepci¾n; RodrĒguez-Arias, Marta; Mi±arro, Jose; Aguilar, Maria A
Multiple high affinity binding sites for 5-hydroxytryptamine: a new class of sites distinct from 5-HT1 and S2.
Two different classes of binding sites probably related to serotonergic receptors have already been reported: 5-HT1 binding sites recognize [3H]5-hydroxytryptamine with a high affinity (Kd = 3 nM) and S2 binding sites recognize [3H]spiroperidol and [3H]ketanserine. An additional population of sites has been observed in crude membrane preparations or fractions enriched with synaptosomal membranes obtained from rat brain cortex. This population was observed as a single class of sites in a synaptosomal fraction (L fraction--according to Laduron (1977)). It corresponded to a dissociation constant Kd = 13-15 nM, and Bmax = 0.80 +/- 0.15 pmol/mg protein. Displacement experiments showed that it recognized preferentially the 5-HT structure (bufotenin, 5-MeO-tryptamine). Tryptamine was a weak displacer and 5,7-dihydroxytryptamine totally inefficient. Neither 8-OH-DPAT, nor quipazine had any effect. Methiothepin, cinanserin and cyproheptadine displaced 5-HT from these sites whereas ergot derivatives did not. Contrary to 5-HT1 binding, this recently observed binding was not altered by GTP; alpha-MSH reduced the corresponding Bmax whereas Leu-enkephalin did not. The degenerative lesion of the serotonergic fibers led to a slight increase in the Bmax of the binding without altering the Kd which means that corresponding sites are not located on serotonergic fibers and might be postsynaptically located. PMID:4052778
Robaut, C; Fillion, M P; Dufois, S; Fayolle-Bauguen, C; Rousselle, J C; Gillet, G; Benkirane, S; Fillion, G
Electrophysiological evidence for rapid 5-HT?A autoreceptor inhibition by vilazodone, a 5-HT?A receptor partial agonist and 5-HT reuptake inhibitor.
This study examined the effect of vilazodone, a combined serotonin (5-HT) reuptake inhibitor and 5-HT(1A) receptor partial agonist, paroxetine and fluoxetine on the sensitivity of 5-HT(1A) autoreceptors of serotonergic dorsal raphe nucleus neurons in rats. These effects were assessed by determining the intravenous dose of (▒)-8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) required to suppress the basal firing rate of these neurons by 50% (ID??) in anesthetized rats using in vivo electrophysiology. 5-HT uptake inhibition was determined by the ability of the compounds to reverse (▒)-p-chloroamphetamine (PCA)-induced rat hypothalamic 5-HT depletion ex vivo. Acute vilazodone administration (0.63 and 2.1 Ąmol/kg, s.c.), compared with vehicle, significantly increased (2-3-fold) the ID?? of 8-OH-DPAT at 4 h, but not 24h after administration. Subchronic administration (3 days) significantly increased the ID?? value at 4 h (3-4-fold) and at 24 h (~2-fold). In contrast, paroxetine and fluoxetine at doses that were supramaximal for 5-HT uptake inhibition did not significantly alter the ID?? value of 8-OH-DPAT after acute or subchronic administration. Vilazodone antagonized the action of PCA 3.5 h and 5 h after a single dose (ID?? 1.49 and 0.46 Ąmol/kg, s.c., respectively), but was inactive 18 h post-administration, corroborating the electrophysiological results at 24 h following acute administration. The results are consistent with the concept of rapid and, following repeated treatment, prolonged inhibition of 5-HT(1A) autoreceptors by vilazodone. This effect could occur by either direct interaction with, or desensitization of, these receptors, an effect which cannot be ascribed to vilazodone's 5-HT reuptake inhibiting properties. PMID:23872377
Ashby, Charles R; Kehne, John H; Bartoszyk, Gerd D; Renda, Matthew J; Athanasiou, Maria; Pierz, Kerri A; Seyfried, Christoph A
F 11356, a novel 5-hydroxytryptamine (5-HT) derivative with potent, selective, and unique high intrinsic activity at 5-HT1B/1D receptors in models relevant to migraine.
F 11356 (4-[4-[2-(2-aminoethyl)-1H-indol-5-yloxyl]acetyl]piperazinyl-1-yl] ben zonitrile) was designed to take advantage of the superior potency and efficacy characteristics of 5-hydroxytryptamine (5-HT) compared with tryptamine at 5-HT1B/1D receptors. F 11356 has subnanomolar affinity for cloned human and nonhuman 5-HT1B and 5-HT1D receptors, and its affinity for 5-HT1A and other 5-HT receptors, including the 5-ht1F subtype, is 50-fold lower and micromolar, respectively. In C6 cells expressing human 5-HT1B or human 5-HT1D receptors, F 11356 was the most potent compound in inhibiting forskolin-induced cyclic AMP formation (pD2 = 8.9 and 9.6), and in contrast to tryptamine and derivatives, it produced maximal enhancement of [35S]guanosine-5'-O-(3-thio)triphosphate-specific binding equivalent to 5-HT. F 11356 was equipotent to 5-HT (pD2 = 7.1 versus 7.2) and more potent than tryptamine derivatives in contracting rabbit isolated saphenous vein. In isolated guinea pig trigeminal ganglion neurons, F 11356 was more potent (pD2 = 7.3 versus 6.7) and induced greater increases in outward hyperpolarizing Ca2+-dependent K+ current than sumatriptan. In anesthetized pigs, F 11356 elicited highly cranioselective, more potent (from 0.16 microgram/kg i.v.) and greater carotid vasoconstriction than tryptamine derivatives. Decreases in carotid blood flow were observed in conscious dogs from 0.63 mg/kg oral F 11356 in the absence of changes in heart rate or behavior. Oral activity was confirmed when hypothermic responses were elicited in guinea pigs (ED50 = 1.6 mg/kg), suggesting that F 11356 also accesses the brain. F 11356 thus is a selective, high-potency agonist at 5-HT1B/1D receptors, which distinguishes itself from tryptamine and derivatives in exerting high intrinsic activity at these receptors in vascular and neuronal models relevant to migraine. PMID:10381763
John, G W; Pauwels, P J; Perez, M; Halazy, S; Le Grand, B; Verscheure, Y; Valentin, J P; Palmier, C; Wurch, T; Chopin, P; Marien, M; Kleven, M S; Koek, W; Assie, M B; Carilla-Durand, E; Tarayre, J P; Colpaert, F C
Emesis and defecations induced by the 5-hydroxytryptamine (5-HT3) receptor antagonist zacopride in the ferret.
Three antiemetic compounds (zacopride, batanopride, granisetron [BRL43694]) were evaluated for the production of gastrointestinal side effects in the conscious ferret after i.v. or p.o. administration. Zacopride evoked multiple emetic and defecatory responses at clinically relevant doses (0.003-0.3 mg/kg) and in a dose-dependent manner. The oral route was the more potent one for eliciting emesis (ED50 0.033 mg/kg). At 0.3 mg/kg p.o., zacopride reliably evoked an 80 to 100% incidence of emesis and a 40 to 80% incidence of defecation. In contrast, batanopride and BRL43694 i.v. evoked a small (10%) incidence of these side effects, but only at 0.1 to 10 mg/kg doses. When given p.o. (0.00003-10 mg/kg), these latter compounds never evoked emesis and significantly reduced (P less than .05) the incidence of defecation below that of vehicle. Responses to zacopride (0.3 mg/kg p.o.) were challenged by i.p. pretreatment with the 5-hydroxytryptamine receptor agonist 2-methyl serotonin, the 5-hydroxytryptamine receptor antagonist BRL43694, the quaternary atropine derivative glycopyrrolate, the dopamine receptor antagonist domperidone or selective abdominal vagotomies. All compounds and either bilateral or dorsal vagotomy significantly reduced the incidence of emesis, but did not abolish it. Latency to first emesis was delayed by BRL43694, domperidone or dorsal vagotomy. The data suggest that the emetic response to p.o. zacopride is mediated in part by 5-hydroxytryptamine receptors residing on either enteric neurons or vagal afferents. However, the underlying pharmacology of the response may also include activation of cholinergic and dopaminergic pathways. PMID:2162943
King, G L
Comparison of the performance of different DFT methods in the calculations of the molecular structure and vibration spectra of serotonin (5-hydroxytryptamine, 5-HT)
NASA Astrophysics Data System (ADS)
Serotonin (5-hydroxytryptamine, 5-HT) is a monoamine neurotransmitter which plays an important role in treating acute or clinical stress. The comparative performance of different density functional theory (DFT) methods at various basis sets in predicting the molecular structure and vibration spectra of serotonin was reported. The calculation results of different methods including mPW1PW91, HCTH, SVWN, PBEPBE, B3PW91 and B3LYP with various basis sets including LANL2DZ, SDD, LANL2MB, 6-31G, 6-311++G and 6-311+G* were compared with the experimental data. It is remarkable that the SVWN/6-311++G and SVWN/6-311+G* levels afford the best quality to predict the structure of serotonin. The results also indicate that PBEPBE/LANL2DZ level show better performance in the vibration spectra prediction of serotonin than other DFT methods.
Yang, Yue; Gao, Hongwei
Constitutive G s-mediated, but not G 12-mediated, activity of the 5-hydroxytryptamine 5HT 7(a) receptor is modulated by the palmitoylation of its C-terminal domain
The 5-HT7 receptor is the most recently described member of the serotonin receptor family. This receptor is mainly expressed in the thalamus, hypothalamus as well as in the hippocampus and cortex. In the present study, we demonstrate that the mouse 5-hydroxytryptamine 5-HT7(a) receptor undergoes post-translational modification by the palmitate, which is covalently attached to the protein through a thioester-type bond.
Elena Kvachnina; Aline Dumuis; Jakub Wlodarczyk; Ute Renner; Maud Cochet; Diethelm W. Richter; Evgeni Ponimaskin
N-{[2-(4-Phenyl-piperazin-1-yl)-ethyl]-phenyl}-arylamides with dopamine D? and 5-Hydroxytryptamine 5HT(1A) activity: synthesis, testing, and molecular modeling.
The ratio of affinities toward the dopamine D? and the 5-hydroxytryptamine 5-HT(1A) receptors is one of the important parameters that determine the efficiency of antipsychotic drugs. Here, we present the synthesis of ortho-, meta-, and para-N-{[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-arylamides and their structure-activity relationship studies on dopamine D? and 5-hydroxytryptamine 5-HT(1A) receptors. It was shown that the biological activity of the described ligands strongly depends on their topology as well as on the nature of the heteroaryl group in the head of the molecules. Docking simulations together with conformational analysis revealed a rational explanation for the ligands' behavior. The molecular model of receptor-ligand interactions described herein provided us with a tool for the rational design of new compounds with a favorable D?/5-HT(1A) profile. PMID:24105736
Sukalovic, Vladimir; Bogdan, Anca Elena; Tovilovic, Gordana; Ignjatovic, Djurdjica; Andric, Deana; Kostic-Rajacic, Sladjana; Soskic, Vukic
Reconsideration of 5-hydroxytryptamine (5-HT)(7) receptor distribution using [(3)H]5-carboxamidotryptamine and [(3)H]8-hydroxy-2-(di-n-propylamino)tetraline: analysis in brain of 5-HT(1A) knockout and 5-HT(1A/1B) double-knockout mice.
The characterization and anatomical distribution of 5-hydroxytryptamine (5-HT)(7) receptor binding sites in brain tissue has been hampered by the lack of a specific radioligand. In the present autoradiographic study, we took advantage of 5-HT(1A) knockout and 5-HT(1A/1B) double-knockout mice to revisit the pharmacological characterization and anatomical localization of 5-HT(7) binding sites in mouse brain using [(3)H]5-carboxamidotryptamine (5-CT) and [(3)H]8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT). The distribution pattern of [(3)H]5-CT binding sites (2 nM) in the brain of mice lacking the 5-HT(1A/1B) receptor was scarce and confined to the septum, globus pallidus, thalamus, hypothalamus, amygdala, cortex, and substantia nigra. The low densities of [(3)H]5-CT binding sites detected in septum, thalamus, hypothalamus, amygdala, and cortex were displaced by 10 microM of the selective 5-HT(7) receptor antagonist (R)-3-(2-(2-(4-methylpiperidin-1-yl) ethyl)pyrrolidine-1-sulfonyl) phenol (SB-269970). The SB-269970-insensitive [(3)H]5-CT binding sites detected in globus pallidus and substantia nigra of 5-HT(1A/1B) knockout mice were displaced by N-[3-(2-dimethylamino)ethoxy-4-methoxy-phenyl]-2'-methyl-4'- (5-methyl-1,2,4-oxadiazol-3-yl)-(1,1'-biphenyl)-4-carboxamide hydrochloride (SB-216641) (1 microM), demonstrating the 5-HT(1D) nature of these binding sites. In contrast to the low densities of [(3)H]5-CT binding sites, high-to-moderate densities of [(3)H]8-OH-DPAT binding sites (10 nM) were found throughout the brain of 5-HT(1A) and 5-HT(1A/1B) knockout mice (olfactory system, septum, thalamus, hypothalamus, amygdala, CA3 field of the hippocampus, cortical mantle, and central gray). These [(3)H]8-OH-DPAT binding sites were displaced by 10 microM SB-269970, risperidone, and methiothepin but not by pindolol, N-tert-butyl-3-[4-(2-methoxyphenyl)piperazin-1-yl]-2-phenylpropanamide (WAY- 100135), or citalopram. We conclude that despite its high affinity for the 5-HT(7) receptor in tissue homogenates, [(3)H]5-CT is not a good tracer for measuring 5-HT(7) receptor binding sites autoradiographically. Also, the lower affinity ligand [(3)H]8-OH-DPAT is a much better tracer for autoradiographic studies at the 5-HT(7) receptor binding sites. PMID:12065723
Bonaventure, Pascal; Nepomuceno, Diane; Kwok, Annette; Chai, Wenying; Langlois, Xavier; Hen, Rene; Stark, Kimberly; Carruthers, Nicholas; Lovenberg, Timothy W
5-Hydroxytryptamine 5HT2C Receptors Form a Protein Complex with N-Methyl-d-aspartate GluN2A Subunits and Activate Phosphorylation of Src Protein to Modulate Motoneuronal Depolarization*
N-Methyl-d-aspartate (NMDA)-gated ion channels are known to play a critical role in motoneuron depolarization, but the molecular mechanisms modulating NMDA activation in the spinal cord are not well understood. This study demonstrates that activated 5HT2C receptors enhance NMDA depolarizations recorded electrophysiologically from motoneurons. Pharmacological studies indicate involvement of Src tyrosine kinase mediates 5HT2C facilitation of NMDA. RT-PCR analysis revealed edited forms of 5HT2C were present in mammalian spinal cord, indicating the availability of G-protein-independent isoforms. Spinal cord neurons treated with the 5HT2C agonist MK 212 showed increased SrcTyr-416 phosphorylation in a dose-dependent manner thus verifying that Src is activated after treatment. In addition, 5HT2C antagonists and tyrosine kinase inhibitors blocked 5HT2C-mediated SrcTyr-416 phosphorylation and also enhanced NMDA-induced motoneuron depolarization. Co-immunoprecipitation of synaptosomal fractions showed that GluN2A, 5HT2C receptors, and Src tyrosine kinase form protein associations in synaptosomes. Moreover, immunohistochemical analysis demonstrated GluN2A and 5HT2C receptors co-localize on the processes of spinal neurons. These findings reveal that a distinct multiprotein complex links 5-hydroxytryptamine-activated intracellular signaling events with NMDA-mediated functional activity.
Bigford, Gregory E.; Chaudhry, Nauman S.; Keane, Robert W.; Holohean, Alice M.
Effects of a selective 5HT reuptake blocker, citalopram, on the sensitivity of 5HT autoreceptors: Electrophysiological studies in the rat brain
Citalopram (CIT), is a selective serotonin (5-HT) reuptake blocker and a clinically effective antidepressant. The present electrophysiological studies were undertaken to investigate in vivo the acute and long-term effects of CIT administration on 5-HT neurotransmission. In a first series of experiments, a single dose of CIT (0.05¢0.5 mg\\/kg) was administered intravenously to naive rats while recording the activity of a
Yves Chaput; Claude de Montigny; Pierre Blier
Adding 5-hydroxytryptamine receptor type 3 antagonists may reduce drug-induced nausea in poor insight obsessive-compulsive patients taking off-label doses of selective serotonin reuptake inhibitors: a 52-week follow-up case report.
Poor-insight obsessive-compulsive disorder (PI-OCD) is a severe form of OCD where the 'typically obsessive' features of intrusive, 'egodystonic' feelings and thoughts are absent. PI-OCD is difficult to treat, often requiring very high doses of serotonergic drugs as well as antipsychotic augmentation. When this occurs, unpleasant side effects as nausea are common, eventually further reducing compliance to medication and increasing the need for pharmacological alternatives. We present the case of a PI-OCD patient who developed severe nausea after response to off-label doses of the selective serotonin reuptake inhibitor (SSRI), fluoxetine. Drug choices are discussed, providing pharmacodynamic rationales and hypotheses along with reports of rating scale scores, administered within a follow-up period of 52 weeks. A slight reduction of fluoxetine dose, augmentation with mirtazapine and a switch from amisulpride to olanzapine led to resolution of nausea while preserving the anti-OCD therapeutic effect. Mirtazapine and olanzapine have already been suggested for OCD treatment, although a lack of evidence exists about their role in the course of PI-OCD. Both mirtazapine and olanzapine also act as 5-hydroxytryptamine receptor type 3 (5-HT3) blockers, making them preferred choices especially in cases of drug-induced nausea. PMID:21143969
Fornaro, Michele; Martino, Matteo
Comparison of effects of a selective 5-HT reuptake inhibitor versus a 5-HT4 receptor agonist on in vivo neurogenesis at the rectal anastomosis in rats.
It was recently reported that activation of enteric neural 5-HT(4) receptors (SR4) promotes reconstruction of enteric neural circuit injury in distal gut of guinea pigs and that this reconstruction involves neural stem cells. We aimed to explore a novel approach using a selective serotonin reuptake inhibitor (SSRI), which increases endogenous 5-HT, to repair enteric nerve fiber injury in the rat distal gut. Enteric nerve fiber injury was performed by rectal transection and subsequent end-to-end one-layer anastomosis. The SSRI fluvoxamine maleate (100 ?mol/l) was applied locally at the anastomotic site to compare with the 5-HT(4) agonist mosapride citrate (100 ?mol/l) (applied for patent) applied locally and orally. Unlike mosapride, fluvoxamine failed to promote the regeneration of the nerve fiber tract across the anastomosis. Furthermore, fluvoxamine did not generate anti-distal-less homeobox 2 (DLX2)- and anti-SR4-positive cells (neural stem cells) and/or anti-neurofilament (NF)-positive cells (neural cells) in newly formed granulation tissue at the anastomosis, whereas these cell types were observed in mosapride-treated preparations. In contrast to its effects in guinea pigs, mosapride generated 5-bromo-2'-deoxyuridine (BrdU)-positive neural cells in ganglia sites 3 mm oral and anal from the anastomosis 2 wk after nerve fiber injury. All actions of mosapride were observed after local and or oral applications. These findings indicate that local SSRI treatment does not induce in vivo nerve fiber tract growth across the anastomosis in the rat distal gut. Mosapride induces nerve fiber tract growth across the anastomosis, mediated through enteric neural stem cells possibly from neural crest-derived stem cells or mesenchymal stem cells in the bone marrow. PMID:22194416
Kawahara, Isao; Kuniyasu, Hiroki; Matsuyoshi, Hiroko; Goto, Kei; Obata, Koji; Misawa, Hiromi; Fujii, Hisao; Takaki, Miyako
The effects of combining serotonin reuptake inhibition and 5-HT7 receptor blockade on circadian rhythm regulation in rodents.
Disruption of circadian rhythms may lead to mood disorders. The present study investigated the potential therapeutic utility of combining a 5-HT7 antagonist with a selective serotonin (5-HT) reuptake inhibitor (SSRI), the standard of care in depression, on circadian rhythm regulation. In tissue explants of the suprachiasmatic nucleus (SCN) from PER2::LUC mice genetically modified to report changes in the expression of a key clock protein, the period length of PER2 bioluminescence was shortened in the presence of AS19, a 5-HT7 partial agonist. This reduction was blocked by SB269970, a selective 5-HT7 antagonist. The SSRI, escitalopram, had no effect alone on period length, but a combination with SB269970, yielded significant increases. Dosed in vivo, escitalopram had little impact on the occurrence of activity onsets in rats given access to running wheels, whether the drug was given acutely or sub-chronically. However, preceding the escitalopram treatment with a single acute dose of SB269970 produced robust phase delays, in keeping with the in vitro explant data. Taken together, these findings suggest that the combination of an SSRI and a 5-HT7 receptor antagonist has a greater impact on circadian rhythms than that observed with either agent alone, and that such a multimodal approach may be of therapeutic value in treating patients with poor clock function. PMID:23276605
Westrich, Ligia; Sprouse, Jeffrey; Sßnchez, Connie
Differential effects of the 5-hydroxytryptamine (5-HT)1A receptor inverse agonists Rec 27/0224 and Rec 27/0074 on electrophysiological responses to 5-HT1A receptor activation in rat dorsal raphe nucleus and hippocampus in vitro.
The pharmacological properties of cyclohexanecarboxylic acid, {2-[4-(2-bromo-5-methoxybenzyl)piperazin-1-yl]ethyl}-(2-trifluoromethoxyphenyl)amide (Rec 27/0224), and cyclohexanecarboxylic acid, (2-methoxy-phenyl)-{2-[4-(2-methoxyphenyl)-piperazin-1-yl]ethyl}amide (Rec 27/0074), were characterized using radioligand displacement and guanosine 5'-O-(3-[35S]thiotriphosphate) ([35S]GTPgammaS) binding assays, as well as electrophysiological experiments, in rat hippocampal and dorsal raphe nucleus (DRN) slices. Both compounds showed a high affinity (Ki, approximately 1 nM) and selectivity (>70-fold) at human 5-hydroxytryptamine (5-HT)1A receptors versus other 5-HT receptors. In [35S]GTPgammaS binding assays on HeLa cells stably expressing human 5-HT1A receptors, Rec 27/0224 and Rec 27/0074 inhibited basal [35S]GTPgammaS binding by 44.8 +/- 1.7% (pEC50 = 8.58) and 25 +/- 2.5% (pEC50 = 8.86), respectively. In intracellularly recorded CA1 pyramidal cells, 5-HT1A (hetero)receptor-mediated hyperpolarization, elicited by 100 nM 5-carboxamidoytryptamine (5-CT), was partially antagonized by Rec 27/0224 (approximately 50%; IC50 = 18.0 nM) and Rec 27/0074 (74%; IC50 = 0.8 nM). In extracellularly recorded DRN serotonergic neurons, Rec 27/0224 and Rec 27/0074 fully antagonized the inhibition of firing caused by the activation of 5-HT1A (auto)receptors by 30 nM 5-CT with an IC50 of 34.9 nM and 16.5 nM, respectively. The antagonism had a slow time course, reaching a steady state within 60 min. Both compounds also antagonized the citalopram-elicited, endogenous 5-HT-mediated inhibition of cell firing. In conclusion, Rec 27/0224 and Rec 27/0074 exhibited inverse agonism in [35S]GTPgammaS binding assays and differential antagonistic properties on 5-HT1A receptor-mediated responses in the hippocampus but not in the DRN. Whether this differential effect is causally related to inverse agonist activity is unclear. The qualitatively different nature of the antagonism in the hippocampus versus the DRN clearly distinguishes the compounds from neutral antagonists, such as N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-2-pyridinylcyclo-hexanecarboxamide (WAY-100635). PMID:15951403
Corradetti, Renato; Mlinar, Boris; Falsini, Chiara; Pugliese, Anna Maria; Cilia, Antonio; Destefani, Carla; Testa, Rodolfo
5HT 7 receptor deletion enhances REM sleep suppression induced by selective serotonin reuptake inhibitors, but not by direct stimulation of 5HT 1A receptor
5-HT7 receptors are involved in REM sleep and possibly in mood disorders. REM sleep suppression and antidepressant-like behavior is observed in 5-HT7?\\/? mice and in rats treated with 5-HT7 receptor antagonists. We recently demonstrated that pharmacological blockade of 5-HT7 receptors enhances REM sleep suppression and antidepressant-like behavior induced by citalopram in rodents. It has been hypothesized that the effect of
Jonathan Shelton; Pascal Bonaventure; Xiaorong Li; Sujin Yun; Timothy Lovenberg; Christine Dugovic
Characterization of the potent 5-HT(1A/B) receptor antagonist and serotonin reuptake inhibitor SB-649915: preclinical evidence for hastened onset of antidepressant/anxiolytic efficacy.
An increase in brain serotonin (5-HT) levels is thought to be a key mechanism of action responsible for generating antidepressant efficacy. It has been proven that selective serotonin reuptake inhibitors are effective antidepressants, but the delay to therapeutic onset of these agents is thought to be due to the time required for 5-HT1A, and possibly 5-HT1B, autoreceptors to desensitize. Therefore, an agent incorporating 5-HT reuptake inhibition coupled with 5-HT1A and/or 5-HT1B autoreceptor antagonism may provide a fast-acting clinical agent. The current studies review the profile of SB-649915 (6-[(1-{2-[(2-methylquinolin-5-yl)oxy]ethyl}piperidin-4-yl)methyl]-2H-1,4-benzoxazin-3(4H)-one), a novel compound with high affinity for human (h) 5-HT1A and 5-HT1B receptors (pKi values of 8.6 and 8.0, respectively) as well as the (h) 5-HT transporter (SERT) (pKi value of 9.3). SB-649915 behaved as an antagonist at both 5-HT1A and 5-HT1B receptors in vitro and in vivo, reversing 5-HT, (+)8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) and SKF99101-induced functional/behavioral responses. Furthermore, it inhibited [3H]5-HT reuptake in rat cortical synaptosomes, in vitro and ex vivo. In electrophysiological studies SB-649915 had no effect on rat dorsal raphe neuronal cell firing per se, but reversed 8-OH-DPAT-induced inhibition of firing both in vitro and in vivo. In addition, in a microdialysis study, it produced an acute increase in extracellular 5-HT in forebrain structures of the rat. Finally, SB-649915 demonstrated acute anxiolytic activity in both rodent and non-human primate and reduced the latency to onset of anxiolytic behavior, compared to paroxetine, in the rat social interaction paradigm. In summary, SB-649915 is a novel, potent 5-HT1A/1B autoreceptor antagonist, and 5-HT reuptake inhibitor. This particular pharmacological profile provides a novel mechanism that could offer fast-acting antidepressant activity. PMID:17627673
Watson, Jeannette M; Dawson, Lee A
Blockade of serotonin 5HT 1B and 5HT 2A receptors suppresses the induction of locomotor activity by 5HT reuptake inhibitors, citalopram and fluvoxamine, in NMRI mice exposed to a novel environment: a comparison to other 5HT receptor subtypes
RationaleĀĀThough 5-HT plays an important role in the modulation of motor function, which is perturbed in depressive states, little is\\u000a known concerning the influence of serotonin reuptake inhibitors (SSRIs) on locomotor activity (LA). Recently, we demonstrated\\u000a that SSRIs, such as citalopram, enhance LA in mice exposed to a novel environment.\\u000a \\u000a \\u000a \\u000a ObjectivesĀĀThis study examined the role of multiple classes of 5-HT
Mark J. Millan; Sylvie Veiga; Sylvie Girardon; Mauricette Brocco
Effects of monoamine reuptake inhibitors on wet-dog shakes mediated by 5-HT2A receptors in ACTH-treated rats.
We examined the influence of imipramine, a serotonin (5-HT) and noradrenaline (NA) reuptake inhibitor, desipramine, a NA reuptake inhibitor, bupropion, a dopamine reuptake inhibitor, fluvoxamine, a selective 5-HT reuptake inhibitor, and mazindol, a catecholamine reuptake inhibitor, on a 5-HT2A receptor-mediated behavior, (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)-induced wet-dog shakes, in naive and adrenocorticotropic hormone (ACTH)-treated rats. Chronic administration of imipramine, desipramine and mazindol suppressed the number of wet-dog shakes in naive rats. Chronic ACTH (100 microg/rat, s.c.) treatment increased the number. Chronic administration of imipramine did not decrease the number of wet-dog shakes in ACTH-treated rats. On the other hand, desipramine and mazindol inhibited the increase in wet-dog shakes in ACTH-treated rats. Fluvoxamine and bupropion did not have any effect on the (+/-)-DOI-induced response in naive and ACTH-treated rats. NA reuptake inhibitors may improve the hyperfunction of 5-HT2A receptors induced by chronic ACTH treatment. PMID:15894065
Kawakami, Yasuhiro; Kitamura, Yoshihisa; Araki, Hiroaki; Kitagawa, Kouhei; Suemaru, Katsuya; Shibata, Kazuhiko; Gomita, Yutaka
Blockade of the high-affinity noradrenaline transporter (NET) by the selective 5-HT reuptake inhibitor escitalopram: an in vivo microdialysis study in mice
BACKGROUND AND PURPOSE Escitalopram, the S(+)-enantiomer of citalopram is the most selective 5-HT reuptake inhibitor approved. Although all 5-HT selective reuptake inhibitors (SSRIs) increase extracellular levels of 5-HT ([5-HT]ext). some also enhance, to a lesser extent, extracellular levels of noradrenaline ([NA]ext). However, the mechanisms by which SSRIs activate noradrenergic transmission in the brain remain to be determined. EXPERIMENTAL APPROACH This study examined the effects of escitalopram, on both [5-HT]ext and [NA]ext in the frontal cortex (FCx) of freely moving wild-type (WT) and mutant mice lacking the 5-HT transporter (SERT?/?) by using intracerebral microdialysis. We explored the possibilities that escitalopram enhances [NA]ext, either by a direct mechanism involving the inhibition of the low- or high-affinity noradrenaline transporters, or by an indirect mechanism promoted by [5-HT]ext elevation. The forced swim test (FST) was used to investigate whether enhancing cortical [5-HT]ext and/or [NA]ext affected the antidepressant-like activity of escitalopram. KEY RESULTS In WT mice, a single systemic administration of escitalopram produced a significant increase in cortical [5-HT]ext and [NA]ext. As expected, escitalopram failed to increase cortical [5-HT]ext in SERT?/? mice, whereas its neurochemical effects on [NA]ext persisted in these mutants. In WT mice subjected to the FST, escitalopram increased swimming parameters without affecting climbing behaviour. Finally, escitalopram, at relevant concentrations, failed to inhibit cortical noradrenaline and 5-HT uptake mediated by low-affinity monoamine transporters. CONCLUSIONS AND IMPLICATIONS These experiments suggest that escitalopram enhances, although moderately, cortical [NA]extin vivo by a direct mechanism involving the inhibition of the high-affinity noradrenaline transporter (NET).
Nguyen, Hai T; Guiard, Bruno P; Bacq, Alexandre; David, Denis J; David, Indira; Quesseveur, Gael; Gautron, Sophie; Sanchez, Connie; Gardier, Alain M
Interactions of N-{[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-2-aryl-2-yl-acetamides and 1-{[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-3-aryl-2-yl-ureas with dopamine D2 and 5-hydroxytryptamine 5HT(1A) receptors.
It is suggested that the ratio of dopamine D(2) to 5-hydroxytryptamine 5-HT(1A) activity is an important parameter that determines the efficiency of antipsychotic drugs. Here we present the synthesis of N-{[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-2-aryl-2-yl-acetamides and 1-{[2-(4-phenyl-piperazin-1-yl)-ethyl]-phenyl}-3-aryl-2-yl-ureas and their structure-activity relationship studies on dopamine D(2) and 5-hydrohytryptamine 5-HT(1A) receptors. It was shown that ligand selectivity and affinity strongly depends on their topology and the presence of a pyridyl group in the head of molecules. Molecular modeling studies using homology modeling and docking simulation revealed a rational explanation for the ligand behavior. The observed binding modes and receptor-ligand interactions provided us with a clue for optimizing the optimal selectivity towards 5-HT(1A) receptors. PMID:22607670
Sukalovic, Vladimir; Ignjatovic, Djurdjica; Tovilovic, Gordana; Andric, Deana; Shakib, Kaveh; Kostic-Rajacic, Sladjana; Soskic, Vukic
Cortical 5-hydroxytryptamine2A-receptor mediated excitatory synaptic currents in the rat following repeated daily fluoxetine administration
Down-regulation of 5-hydroxytryptamine2A (5-HT2A) receptors has been a consistent effect induced by most antidepressant drugs. The evidence for down-regulation of 5-HT2A receptor binding following subchronic treatment with fluoxetine and other selective serotonin reuptake inhibitors (SSRIs) is mixed. The question of 5-HT2A receptor sensitivity during chronic administration of antidepressants is important since activation of 5-HT2A receptors is associated with impulsivity. Continued activation of 5-HT2A receptors may functionally oppose activation of other non-5-HT2A receptors in the prefrontal cortex associated with the clinical efficacy of SSRI treatment. Therefore, the effects of repeated daily administration of fluoxetine (10 mg/kg, i.p. ū 3 weeks) on pharmacologically characterized electrophysiological response mediated by 5-HT2A receptor activation, 5-HT-induced excitatory postsynaptic currents (EPSCs), in rat prefrontal cortical slices was examined. The concentration-response curve for 5-HT-induced EPSCs was unchanged following subchronic fluoxetine treatment. This subchronic fluoxetine treatment failed to modify electrophysiological responses to AMPA in layer V pyramidal cells as well. These findings would be consistent with the hypothesis that blockade of 5-HT2A receptors may enhance the effects of SSRIs or serotonin/norepinephrine reuptake inhibitors (SNRIs).
Marek, Gerard J.
Multiparameter Optimization in CNS Drug Discovery: Design of Pyrimido[4,5-d]azepines as Potent 5-Hydroxytryptamine 2C (5-HT2C) Receptor Agonists with Exquisite Functional Selectivity over 5-HT2A and 5-HT2B Receptors.
A series of 4-substituted pyrimido[4,5-d]azepines that are potent, selective 5-HT2C receptor partial agonists is described. A rational medicinal chemistry design strategy to deliver CNS penetration coupled with SAR-based optimization of selectivity and agonist potency provided compounds with the desired balance of preclinical properties. Lead compounds 17 (PF-4479745) and 18 (PF-4522654) displayed robust pharmacology in a preclinical canine model of stress urinary incontinence (SUI) and no measurable functional agonism at the key selectivity targets 5-HT2A and 5-HT2B in relevant tissue-based assay systems. Utilizing recent advances in the structural biology of GPCRs, homology modeling has been carried out to rationalize binding and agonist efficacy of these compounds. PMID:24878222
Storer, R Ian; Brennan, Paul E; Brown, Alan D; Bungay, Peter J; Conlon, Kelly M; Corbett, Matthew S; DePianta, Robert P; Fish, Paul V; Heifetz, Alexander; Ho, Danny K H; Jessiman, Alan S; McMurray, Gordon; de Oliveira, Cesar Augusto F; Roberts, Lee R; Root, James A; Shanmugasundaram, Veerabahu; Shapiro, Michael J; Skerten, Melanie; Westbrook, Dominique; Wheeler, Simon; Whitlock, Gavin A; Wright, John
Effects of chronically administered venlafaxine on 5-HT receptor activity in rat hippocampus and hypothalamus.
The effects of chronic administration of the mixed serotonin [5-hydroxytryptamine (5-HT)]/norepinephrine re-uptake inhibitor venlafaxine (5 mg/kg daily by osmotic minipump for 28 days) on the sensitivity of somatodendritic 5-HT(1A) autoreceptors on serotonergic neurons innervating the hypothalamus, and on 5-HT(1B) autoreceptors in both hypothalamus and hippocampus, were determined using in vivo microdialysis in freely moving rats. Venlafaxine induced a reduction in sensitivity of 5-HT(1B) autoreceptors in hypothalamus, but did not affect the sensitivity of 5-HT(1A) autoreceptors, or of 5-HT(1B) autoreceptors in hippocampus. The corticosterone and oxytocin responses to the 5-HT(1A) receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT, 0.05 or 0.2 mg/kg), a measure of postsynaptic 5-HT(1A) receptor activity in the hypothalamus, were reduced in animals administered 5 or 10 mg/kg venlafaxine daily by intraperitoneal injection for 21 days. This desensitization of post-synaptic 5- HT(1A) receptors in the hypothalamus may be a consequence of increased 5-HT levels induced by desensitization of the presynaptic 5-HT(1B) receptors. These results taken together with those of previous studies suggest that the hypothalamus might be an important site of drug action, and that venlafaxine has an overall mechanism similar to that of selective serotonin re-uptake inhibitors. PMID:11834247
Gur, Eitan; Dremencov, Eliyahu; Van De Kar, Louis D; Lerer, Bernard; Newman, Michael E
Endogenous Serotonin Excites Striatal Cholinergic Interneurons via the Activation of 5HT 2C, 5HT6, and 5HT7 Serotonin Receptors: Implications for Extrapyramidal Side Effects of Serotonin Reuptake Inhibitors
The striatum is richly innervated by serotonergic afferents from the raphe nucleus. We explored the effects of this input on striatal cholinergic interneurons from rat brain slices, by means of both conventional intracellular and whole-cell patch-clamp recordings. Bath-applied serotonin (5-HT, 3¢300 ?M), induced a dose-dependent membrane depolarization and increased the rate of spiking. This effect was mimicked by the 5-HT
Paola Bonsi; Dario Cuomo; Jun Ding; Giuseppe Sciamanna; Sasha Ulrich; Anne Tscherter; Giorgio Bernardi; D James Surmeier; Antonio Pisani
Clinical evidence for serotonin and norepinephrine reuptake inhibition of duloxetine.
Most antidepressants in clinical use are believed to function by enhancing neurotransmission of serotonin [5-hydroxytryptamine (5-HT)] and/or norepinephrine (NE) via inhibition of neurotransmitter reuptake. Agents that affect reuptake of both 5-HT and NE (serotonin-norepinephrine reuptake inhibitors) have been postulated to offer greater efficacy for the treatment of major depressive disorder (MDD). These dual-acting agents also display a broader spectrum of action, including efficacy for MDD and associated painful physical symptoms, diabetic peripheral neuropathic pain, generalized anxiety disorder, and fibromyalgia syndrome. Substantial preclinical evidence shows that duloxetine, an approved drug for the treatment of MDD, generalized anxiety disorder, and the management of diabetic peripheral neuropathic pain, inhibits reuptake of both 5-HT and NE. This paper reviews clinical and neurochemical evidence of duloxetine's effects on 5-HT and NE reuptake inhibition. The clinical evidence supporting duloxetine's effects on NE reuptake inhibition includes indirect measures such as altered excretion of NE metabolites, cardiovascular effects, and treatment-emergent adverse event profiles similar to those for other drugs believed to act through the inhibition of NE reuptake. In summary, the data presented in this report provide clinical evidence of a mechanism for duloxetine involving both 5-HT and NE reuptake inhibition in humans and are consistent with preclinical evidence for 5-HT/NE reuptake inhibition. PMID:18408530
Trivedi, Madhukar H; Desaiah, Durisala; Ossanna, Melissa J; Pritchett, Yili L; Brannan, Stephen K; Detke, Michael J
In vitro neuronal and vascular responses to 5-HT in rats chronically exposed to MDMA
This study examined the effects of chronic exposure of rats to 3,4-methylenedioxymethamphetamine (MDMA) on [3H]5-hydroxytryptamine ([3H]5-HT) re-uptake into purified rat brain synaptosomes, 5-HT-induced isometric contraction of aortic rings and [3H]5-HT re-uptake into rat aorta.Rats were administered MDMA (20?mg?kg?1 i.p.) twice daily over 4 days. One, 7, 14 or 21 days post treatment, whole brain synaptosomes and descending thoracic aortic rings were prepared for investigation.Chronic MDMA treatment significantly reduced the maximum rate (Vmax) of specific high-affinity [3H]5-HT re-uptake 1 day after treatment and for up to 21 days post-final administration of MDMA. Direct application of MDMA (100??M) abolished synaptosomal re-uptake of [3H]5-HT in vitro.Chronic MDMA administration significantly reduced the maximum contraction (Emax) to 5-HT at 1 and 7 days after treatment, but not at 14 or 21 days.Chronic MDMA administration had no effect on sodium-dependent [3H]5-HT re-uptake into aorta 1 day after treatment, nor did 100??M MDMA have any direct effect on [3H]5-HT uptake into aortic rings in vitro.These results show, for the first time, an altered responsiveness of vascular tissue to MDMA after chronic administration. In addition, they demonstrate a difference in the sensitivity of central and peripheral 5-HT uptake systems to chronic MDMA exposure, and suggest that the action of MDMA in the cardiovascular system does not arise from a direct effect of MDMA on peripheral 5-HT transport.
Cannon, Dara M; Keenan, Alan K; Guiry, Patrick J; Buon, Christophe; Baird, Alan W; McBean, Gethin J
5-Hydroxytryptamine (serotonin) in the gastrointestinal tract
Purpose of review Although the gut contains most of the bodyÆs 5-hydroxytryptamine (5-HT), many of its most important functions have recently been discovered. This review summarizes and directs attention to this new burst of knowledge. Recent findings Enteroendocrine cells have classically been regarded as pressure sensors, which secrete 5-HT to initiate peristaltic reflexes; nevertheless, recent data obtained from studies of mice that selectively lack 5-HT either in enterochromaffin cells (deletion of tryptophan hydroxylase 1 knockout; TPH1KO) or neurons (TPH2KO) imply that neuronal 5-HT is more important for constitutive gastrointestinal transit than that of enteroendocrine cells. The enteric nervous system of TPH2KO mice, however, also lacks a full complement of neurons; therefore, it is not clear whether slow transit in TPH2KO animals is due to their neuronal deficiency or absence of serotonergic neurotransmission. Neuronal 5-HT promotes the growth/maintenance of the mucosa as well as neurogenesis. Enteroendocrine cell derived 5-HT is an essential component of the gastrointestinal inflammatory response; thus, deletion of the serotonin transporter increases, whereas TPH1KO decreases the severity of intestinal inflammation. Enteroendocrine cell derived 5-HT, moreover, is also a hormone, which inhibits osteoblast proliferation and promotes hepatic regeneration. Summary New studies show that enteric 5-HT is a polyfunctional signalling molecule, acting both in developing and mature animals as a neurotransmitter paracrine factor, endocrine hormone and growth factor.
Gershon, Michael D.
Memory time-course: mRNA 5HT 1A and 5HT 7 receptors
In an attempt to clarify conflicting results about serotonin (5-hydroxytryptamine, 5-HT) 5-HT1A and 5-HT7 receptors in memory formation, their mRNA expression was determined by RT-PCR in key brain areas for explicit and implicit memory. The time-course (0¢120h) of autoshaped responses was progressive and mRNA 5-HT1A or 5-HT7 receptors expression monotonically augmented or declined in prefrontal cortex, hippocampus and raphe nuclei,
Georgina Perez-Garcia; Alfredo Meneses
5-Hydroxytryptamine type 3 (5-HT3) receptors are cation-selective Cys loop receptors found in both the central and peripheral nervous systems. There are five 5-HT3 receptor subunits (A¢E), and all functional receptors require at least one A subunit. Regions from noncontiguous parts of the subunit sequence contribute to the agonist-binding site, and the roles of a range of amino acid residues that form the binding pocket have been identified. Drugs that selectively antagonize 5-HT3 receptors (the ōsetronsö) are the current gold standard for treatment of chemotherapy-induced and postoperative nausea and vomiting and have potential for the treatment of a range of other conditions.
Lummis, Sarah C. R.
Allosteric regulation by oleamide of the binding properties of 5-hydroxytryptamine 7 receptors
Oleamide belongs to a family of amidated lipids with diverse biological activities, including sleep induction and signaling modulation of several 5-hydroxytryptamine (5-HT) receptor subtypes, including 5-HT1A, 5-HT2A\\/2C, and 5-HT7. The 5-HT7 receptor, predominantly localized in the hypothalamus, hippocampus, and frontal cortex, stimulates cyclic AMP formation and is thought to be involved in the regulation of sleep¢wake cycles. Recently, it was
Peter B Hedlund; Monica J Carson; J. Gregor Sutcliffe; Elizabeth A Thomas
Pharmacological and Molecular Characterization of 5- Hydroxytryptamine7 Receptors in the Rat Adrenal Gland
Serotonin (5-hydroxytryptamine; 5-HT) is a potent stimulator of aldosterone secretion in the rat adrenal gland but the type of receptor involved in the mechanism of action of 5-HT remains unknown. The aim of the present study was to determine the pharmacological profile and to clone the receptor responsible for the corticotropic effect of 5-HT in rat glomerulosa cells. A series
Anti-emetic effect of mosapride citrate hydrate, a 5-HT4 receptor agonist, on selective serotonin reuptake inhibitors (SSRIs)-induced emesis in experimental animals.
Although selective serotonin reuptake inhibitors (SSRIs) are widely used to treat depression, they frequently cause gastrointestinal adverse effects, such as nausea and emesis. In the present study, we investigated the anti-emetic effect of mosapride, a 5-HT(4) receptor agonist, on SSRIs-induced emesis in Suncus murinus and dogs. We also examined the effect of mosapride on SSRIs-induced delay in gastric emptying and increase in gastric vagal afferent activity in rats. Oral administration of paroxetine, but not its subcutaneous administration, dose-dependently caused emesis in both animals. Mosapride inhibited paroxetine-induced emesis in Suncus murinus and dogs with ID(50) values of 7.9 and 1.1 mg/kg, respectively. The anti-emetic effect of mosapride was partially inhibited by SB207266, a selective 5-HT(4) antagonist. Intragastric administration of paroxetine increased gastric vagal afferent discharge in anesthetized rats. Mosapride failed to suppress this increase. On the other hands, mosapride improved the delay in gastric emptying caused by paroxetine in rats. We have shown in this study that oral administration of SSRIs causes emesis and activates gastric vagal afferent activity in experimental animals and that mosapride inhibits SSRIs-induced emesis, probably via improvement of SSRIs-induced delay in gastric emptying. These findings highlight the promising potential of mosapride as an anti-emetic agent. PMID:23257657
Mine, Yukiko; Oku, Seiko; Yoshida, Naoyuki
Measuring endogenous 5-HT release by emission tomography: promises and pitfalls
Molecular in vivo neuroimaging techniques can be used to measure regional changes in endogenous neurotransmitters, evoked by challenges that alter synaptic neurotransmitter concentration. This technique has most successfully been applied to the study of endogenous dopamine release using positron emission tomography, but has not yet been adequately extended to other neurotransmitter systems. This review focuses on how the technique has been applied to the study of the 5-hydroxytryptamine (5-HT) system. The principles behind visualising fluctuations in neurotransmitters are introduced, with reference to the dopaminergic system. Studies that aim to image acute, endogenous 5-HT release or depletion at 5-HT receptor targets are summarised, with particular attention to studies in humans. Radiotracers targeting the 5-HT1A, 5-HT2A, and 5-HT4 receptors and the serotonin reuptake transporter have been explored for their sensitivity to 5-HT fluctuations, but with mixed outcomes; tracers for these targets cannot reliably image endogenous 5-HT in humans. Shortcomings in our basic knowledge of the mechanisms underlying changes in binding potential are addressed, and suggestions are made as to how the selection of targets, radiotracers, challenge paradigms, and experimental design might be optimised to improve our chances of successfully imaging endogenous neurotransmitters in the future.
Paterson, Louise M; Tyacke, Robin J; Nutt, David J; Knudsen, Gitte M
5HT Receptor-Associated Proteins (FRAPs)
Dysfunction in the serotonergic system contributes to the etiology and pathophysiology of a variety of neuropsychiatric and\\u000a systemic disorders, and 5-hydroxytryptamine(5-HT) receptors as a group represent important therapeutic targets for many of\\u000a these debilitating diseases. Encompassing a diverse group of proteins that interact with 5-HT receptors, 5-HT receptor-associated\\u000a proteins (FRAPs) coordinate receptor targeting to the appropriate subcellular compartments, organization of
Zongqi Xia; Douglas J. Sheffler; Bryan L. Roth
5HT 3 receptor antagonists and migraine therapy
Summary Neuronal 5-hydroxytryptamine3 (5-HT3) receptors mediate the excitatory effects of 5-HT. They are located in pain- and nausea-modulating areas in the central nervous system and on C-fibre primary afferents in the peripheral nervous system. Consequently, these receptors mediate the painful and emetic effects of 5-HT. Selective and potent 5-HT3 receptor antagonists have been shown to block inflammatory and 5-HT induced
M. D. Ferrari
Identification of the adenylyl cyclase-activating 5-hydroxytryptamine receptor subtypes expressed in the rat submandibular gland
1 Serotonin (5-hydroxytryptamine, 5-HT) has been shown to increase cyclic AMP production in dispersed cell aggregates from the major salivary glands of the rat. The goal of the present study was to identify the 5-HT receptor subtypes that mediate these e─ects in rat submandibular glands (SMG). 2 Among the 5-HT receptor subtypes identified in the rat, 5-HT4(a,b), 5-HT6 and 5-HT7(a,b,c)
D. M. Bourdon; J. M. Camden; L. A. Landon; F. O. Levy; J. T. Turner
The 5-hydroxytryptamine 4 receptor agonist mosapride does not antagonize morphine-induced respiratory depression
Background: On the basis of experiments in rats, serotonin 4 receptor (5-hydroxytryptamine 4 [5-HT4]) agonists have been proposed as a novel therapeutic strategy for the selective treatment of respiratory depression caused by opioids while leaving analgesic effects unaffected. The effects in rats have been seen with the 5-hydroxytryptamine 4a (5-HT4a) agonist BIMU8, which is currently not available for use in
J÷rn L÷tsch; Carsten Skarke; Andreas Schneider; Thomas Hummel; Gerd Geisslinger
Effects of milnacipran, a 5-HT and noradrenaline reuptake inhibitor, on C-fibre-evoked field potentials in spinal long-term potentiation and neuropathic pain
BACKGROUND AND PURPOSE The analgesic action of 5-HT and noradrenaline reuptake inhibitors (SNRIs) on nociceptive synaptic transmission in the spinal cord is poorly understood. We investigated the effects of milnacipran, an SNRI, on C-fibre-evoked field potentials (FPs) in spinal long-term potentiation (LTP), a proposed synaptic mechanism of hypersensitivity, and on the FPs in a neuropathic pain model. EXPERIMENTAL APPROACH C-fibre-evoked FPs by electrical stimulation of the sciatic nerve fibres were recorded in the spinal dorsal horn of anaesthetized adult rats, and LTP was induced by high-frequency stimulation of the sciatic nerve fibres. A rat model of neuropathic pain was produced by L5 spinal nerve ligation and transection. KEY RESULTS Milnacipran produced prolonged inhibition of C-fibre-evoked FPs when applied spinally after the establishment of LTP of C-fibre-evoked FPs in na've animals. In the neuropathic pain model, spinal administration of milnacipran clearly reduced the basal C-fibre-evoked FPs. These inhibitory effects of milnacipran were blocked by spinal administration of methysergide, a 5-HT1/2 receptor antagonist, and yohimbine or idazoxan, ?2-adrenoceptor antagonists. However, spinal administration of milnacipran in na've animals did not affect the basal C-fibre-evoked FPs and the induction of spinal LTP. CONCLUSION AND IMPLICATIONS Milnacipran inhibited C-fibre-mediated nociceptive synaptic transmission in the spinal dorsal horn after the establishment of spinal LTP and in the neuropathic pain model, by activating both spinal 5-hydroxytryptaminergic and noradrenergic systems. The condition-dependent inhibition of the C-fibre-mediated transmission by milnacipran could provide novel evidence regarding the analgesic mechanisms of SNRIs in chronic pain.
Ohnami, S; Kato, A; Ogawa, K; Shinohara, S; Ono, H; Tanabe, M
Effects of reserpine and chlorpromazine on 5-hydroxytryptamine uptake of platelets from migrainous and control subjects
Platelet aggregation experiments confirm differences between the 5-hydroxytryptamine (5-HT) receptors of migrainous and control platelets. However, no differences have been found in 5-HT uptake, in the presence of reserpine or chlorpromazine, into migrainous and control platelets. The results support the hypothesis that receptors for 5-HT induced platelet aggregation provide a model for vascular receptors causing constriction and are distinct from those transferring 5-HT through the platelet membrane.
Hilton, Barbara P.
The Failure of Buffered 5-Hydroxytryptamine to Increase Brain Capillary Permeability to Albumin.
National Technical Information Service (NTIS)
The effect of buffered 5-hydroxytryptamine (5-HT) on the blood-brain barrier to 125I-albumin was studied in 14 rhesus monkeys. 5-HT was introduced into the lateral ventricle by ventriculocisternal perfusion resulting in a concentration gradient in the per...
L. S. Solomon
5HT7 receptors are involved in mediating 5HT-induced activation of rat primary afferent neurons
The purpose of this study was to determine whether the 5-hydroxytryptamine7 (5-HT7) receptor is expressed by nociceptor-like neurons in the rat PNS and whether 5-HT activates these nociceptors via the 5-HT7 receptor subtype. Using a polyclonal antibody and the method of immunofluorescence staining, we demonstrated that the 5-HT7 receptor appears predominately on ōnociceptor-likeö neurons of the rat lumbar dorsal root
Thomas Meuser; Christian Pietruck; Anja Gabriel; Guo-Xi Xie; Kyung-Joon Lim; Pamela Pierce Palmer
Functional expression of 5-HT{sub 2A} receptor in osteoblastic MC3T3-E1 cells
In the previous study, we reported the gene expression for proteins related to the function of 5-hydroxytryptamine (5-HT, serotonin) and elucidated the expression patterns of 5-HT{sub 2} receptor subtypes in mouse osteoblasts. In the present study, we evaluated the possible involvement of 5-HT receptor subtypes and its inactivation system in MC3T3-E1 cells, an osteoblast cell line. DOI, a 5-HT{sub 2A} and 5-HT{sub 2C} receptor selective agonist, as well as 5-HT concentration-dependently increased proliferative activities of MC3T3-E1 cells in their premature period. This effect of 5-HT on cell proliferation were inhibited by ketanserin, a 5-HT{sub 2A} receptor specific antagonist. Moreover, both DOI-induced cell proliferation and phosphorylation of ERK1 and 2 proteins were inhibited by PD98059 and U0126, selective inhibitors of MEK in a concentration-dependent manner. Furthermore, treatment with fluoxetine, a 5-HT specific re-uptake inhibitor which inactivate the function of extracellular 5-HT, significantly increased the proliferative activities of MC3T3-E1 cells in a concentration-dependent manner. Our data indicate that 5-HT fill the role for proliferation of osteoblast cells in their premature period. Notably, 5-HT{sub 2A} receptor may be functionally expressed to regulate mechanisms underlying osteoblast cell proliferation, at least in part, through activation of ERK/MAPK pathways in MC3T3-E1 cells.
Hirai, Takao; Kaneshige, Kota; Kurosaki, Teruko [Department of Molecular Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 1 Gakuen-cho, Fukuyama, Hiroshima 729-0292 (Japan)] [Department of Molecular Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 1 Gakuen-cho, Fukuyama, Hiroshima 729-0292 (Japan); Nishio, Hiroaki, E-mail: email@example.com [Department of Molecular Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 1 Gakuen-cho, Fukuyama, Hiroshima 729-0292 (Japan)] [Department of Molecular Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 1 Gakuen-cho, Fukuyama, Hiroshima 729-0292 (Japan)
Recent advances in understanding the role of serotonin in gastrointestinal motility in functional bowel disorders: alterations in 5-HT signalling and metabolism in human disease.
Serotonin (5-hydroxytryptamine, 5-HT) is present in abundance within the gut, most stored in enterochromaffin cell granules. It is released by a range of stimuli, most potently by mucosal stroking. Released 5-HT stimulates local enteric nervous reflexes to initiate secretion and propulsive motility. It also acts on vagal afferents altering motility and in large amounts induces nausea. Rapid reuptake by a specific transporter (serotonin transporter, SERT) limits its diffusion and actions. Abnormally increased 5-HT is found in a range of gastrointestinal disorders including chemotherapy-induced nausea and vomiting, carcinoid syndrome, coeliac disease, inflammatory bowel disease and irritable bowel syndrome (IBS) with diarrhoea (IBS-D), especially that developing following enteric infection. Impaired SERT has been described in IBS-D and might account for some of the increase in mucosal 5-HT availability. 5-HT(3) receptor antagonists inhibit chemotherapy-induced nausea and diarrhoea associated with both carcinoid syndrome and IBS. While IBS-D is associated with increased 5-HT postprandially, IBS with constipation (IBS-C) is associated with impaired 5-HT response and responds to 5-HT(4) agonists such as Prucalopride and 5-HT(4) partial agonists such as Tegaserod. PMID:17620085
Spiller, R
Characterization of 5-hydroxytryptamine 1A properties of flesinoxan: In Vivo electrophysiology and hypothermia study
Flesinoxan is a high affinity and selective 5-hydroxytryptamine1A (5-HT1A) ligand which, unlike the 5-HT1A agonists of the azapirone class, does not generate l-(2-pyrimidinyl)piperazine, an ?2-adrenoreceptor antagonist. In view of potential antidepressant effects of flesinoxan, this study was undertaken to characterize its 5-HT1A properties in the rat brain using in vivo electrophysiology and hypothermia paradigms. The suppressant effect of microiontophoretic applications
V. Hadrava; P. Blier; T. Dennis; C. Ortemann; C. De Montigny
The interaction of some kynurenine pathway metabolites with 5-hydroxytryptophan and 5-hydroxytryptamine
The kynrenine pathway metabolites kynurenine, 3-hydroxykynurenine and xanthurenic acid have been tested against 5-hydroxytryptamine (5-HT) and 5-hydroxytryptophan (5-HTP)-induced head twitches in the mouse in a dose-range of 0.5¢5.0 mg\\/kg. Kynurenine and 3-hydroxykynurenine were highly active. Low doses caused marked potentiation of the twitch response to both 5-HT and 5-HTP with increased toxicity of 5-HT. High doses caused antagonism of both
Sheila L. Handley; Ruth C. Miskin
Postprandial plasma 5-hydroxytryptamine in diarrhoea predominant irritable bowel syndrome: a pilot study
BackgroundŚIncreased concentrations of 5-hydroxytryptamine (5-HT) can be detected in the systemic circulation after a meal and may be involved in the physiological control of gastrointestinal motility. Abnormalities of 5-HT release after a meal might explain some of the postprandial symptoms associated with the irritable bowel syndrome (IBS).AimŚTo investigate the effect of a standard meal on plasma 5-HT and urinary 5-hydroxyindole
C P Bearcroft; D Perrett; M J G Farthing
Release of ( sup 14 C)5-hydroxytryptamine from human platelets by red wine
Red wine, at a final dilution of 1/50, caused released of ({sup 14}C)5-hydroxytryptamine (5-HT) from preloaded platelets, an effect which was not observed with any white wines or beers tested. Since 5-HT, is probably released from body stores during migraine attacks and red wine is known to provoke migraine episodes in susceptible individuals, release of 5-HT, possibly from central stores, could represent a plausible mechanism for its mode of action.
Jarman, J.; Glover, V.; Sandler, M. (Queen Charlotte's and Chelsea Hospital, London (England))
Release of ( sup 14 C)5-hydroxytryptamine from human platelets by red wine
Red wine, at a final dilution of 1\\/50, caused released of (┬╣Ōü┤C)5-hydroxytryptamine (5-HT) from preloaded platelets, an effect which was not observed with any white wines or beers tested. Since 5-HT, is probably released from body stores during migraine attacks and red wine is known to provoke migraine episodes in susceptible individuals, release of 5-HT, possibly from central stores, could
J. Jarman; V. Glover; M. Sandler
Ketanserin causes surmountable antagonism of 5-hydroxytryptamine-induced contractions of large coronary arteries of dog.
Large coronary arteries of the dog were contracted with 5-hydroxytryptamine (5-HT). The 5-HT2-receptor antagonist ketanserin antagonized the 5-HT-induced effects. Unlike Brazenor and Angus (Europ J Pharmacol 81:569-576, 1982) who reported insurmountable antagonism of the effects of 5-HT in dog coronaries, we found that the antagonism by ketanserin can be surmounted, provided the concentrations of 5-HT are high enough. Ketanserin also unmasked a saturable component of the 5-HT-induced contractions. Although ketanserin (0.1-1 mumol/l) depressed the maximal force of the saturable component, it did not change its EC50 (-log mol/l 8.0). We conclude that large coronary arteries of dog are contracted by 5-HT mainly through 5-HT2-receptors and to a smaller extent through receptors different from 5-HT2. PMID:3157065
Frenken, M; Kaumann, A J
Characteristics of 5-Hydroxytryptamine Receptors Involved in Contraction of Feline Ileal Longitudinal Smooth Muscle
A number of studies have demonstrated that 5-hydroxytryptamine (5-HT) can induce muscle contraction or relaxation response and enhance secretion in the gastrointestinal tract via a multiplicity of 5-HT receptor subtypes. In the present study, we investigated the pharmacological characterization of the 5-HT-induced contractile response in longitudinal smooth muscle isolated from the feline ileum. Addition of 5-HT into muscle chambers enhanced the basal tone and spontaneous activity in a concentration-dependent manner. The neurotoxin tetrodotoxin did not alter the 5-HT-induced contraction of the longitudinal muscles. Neither atropine nor guanethidine affected the contraction. The 5-HT agonists, 5-methylserotonin hydrochloride and mosapride, also evoked concentration-dependent contractions. The 5-HT-induced contraction was enhanced by the 5HT2 receptor antagonist ketanserin and the 5-HT3 receptor antagonist ondansetron but was inhibited by the 5-HT1 receptor antagonist methysergide and 5-HT4 receptor antagonist GR113808. These results indicate that 5-HT1 and 5-HT4 receptors may mediate the contraction of the 5-HT-induced response and 5-HT2 and 5-HT3 receptors may mediate 5-HT-induced relaxation in feline ileal longitudinal smooth muscles.
Wang, YiYi; Park, Sun Young; Oh, Kyung Hoon; Min, Youngsil; Lee, Yun-Jeong; Lee, Seok-Yong
Characteristics of 5-hydroxytryptamine receptors involved in contraction of feline ileal longitudinal smooth muscle.
A number of studies have demonstrated that 5-hydroxytryptamine (5-HT) can induce muscle contraction or relaxation response and enhance secretion in the gastrointestinal tract via a multiplicity of 5-HT receptor subtypes. In the present study, we investigated the pharmacological characterization of the 5-HT-induced contractile response in longitudinal smooth muscle isolated from the feline ileum. Addition of 5-HT into muscle chambers enhanced the basal tone and spontaneous activity in a concentration-dependent manner. The neurotoxin tetrodotoxin did not alter the 5-HT-induced contraction of the longitudinal muscles. Neither atropine nor guanethidine affected the contraction. The 5-HT agonists, 5-methylserotonin hydrochloride and mosapride, also evoked concentration-dependent contractions. The 5-HT-induced contraction was enhanced by the 5HT(2) receptor antagonist ketanserin and the 5-HT(3) receptor antagonist ondansetron but was inhibited by the 5-HT(1) receptor antagonist methysergide and 5-HT(4) receptor antagonist GR113808. These results indicate that 5-HT(1) and 5-HT(4) receptors may mediate the contraction of the 5-HT-induced response and 5-HT(2) and 5-HT(3) receptors may mediate 5-HT-induced relaxation in feline ileal longitudinal smooth muscles. PMID:22128258
Wang, Yiyi; Park, Sun Young; Oh, Kyung Hoon; Min, Youngsil; Lee, Yun-Jeong; Lee, Seok-Yong; Sohn, Uy Dong
Role of peripheral 5HT 4, 5HT 6, and 5HT 7 receptors in development and maintenance of secondary mechanical allodynia and hyperalgesia
The role of 5-hydroxytryptamine (5-HT)4, 5-HT6, and 5-HT7 receptors in formalin-induced secondary allodynia and hyperalgesia in rats was assessed. Formalin produced acute nociceptive behaviors (flinching and licking\\/lifting) followed by long-term secondary mechanical allodynia and hyperalgesia. Pretreatment (?10min) with cromoglycate (195¢1950nmol\\/paw) partially inhibited acute nociceptive behaviors and completely prevented secondary allodynia and hyperalgesia on day 6 after injection. Ipsilateral peripheral pretreatment
Beatriz GodĒnez-Chaparro; Paulino Barragßn-Iglesias; Gabriela Casta±eda-Corral; Hķctor I. Rocha-Gonzßlez; Vinicio Granados-Soto
[The 5-HT1A receptor: a new effective principle in psychopharmacologic therapy?].
The 5-hydroxytryptamine (5-HT)1A receptor has been the focus of considerable research effort over a decade. However, the definitive classification of this receptor and the full characterization of its pharmacology is still in progress. On the one hand, the selective serotonin-1A receptor partial agonist anxiolytics were developed first and represented a new class of pharmacological agents that have demonstrated efficacy in the treatment of generalized anxiety disorder (GAD). These compounds (e.g. buspirone, gepirone, tandospirone or ipsapirone) offered a completely different pharmacologic approach to this disorder from previous medications as benzodiazepines or alcohol. On the other hand, beta-adrenoceptor blockers (e.g. [-]-pindolol, [-]-propranolol) have been shown to have antagonistic properties on the 5-HT1A receptor side. Preliminary results suggest that beta-adrenoceptor blockers may be useful as adjunctive medication in the treatment of depression by augmenting the antidepressant efficacy of selective serotonin reuptake inhibitors. As the beta-adrenoceptor blockers show also affinities to other 5-HT receptors than the 5-HT1A receptor the recently discovered more selective 5-HT1A antagonists became of interest. The pharmacological properties and potential therapeutic utility of these novel compounds will also be discussed. PMID:9064274
Davids, E; Lesch, K P
The gastrointestinal prokinetic benzamide derivatives are agonists at the non-classical 5HT receptor (5HT 4 ) positively coupled to adenylate cyclase in neurons
We have previously shown that a non-classical 5-hydroxytryptamine (5-HT4) receptor mediates the stimulation of adenylate cyclase activity in mouse embryo colliculi neurons in primary culture. The pharmacological characteristics of this receptor exclude the possibility that it belongs to the known 5-HT1, 5-HT2 or 5-HT3 receptor types. Here we report that this 5-HT receptor can be stimulated by 4-amino-5-chloro-2-methoxy substituted benzamide
Aline Dumuis; MichĶle Sebben; Joļl Bockaert
Assessment of 5-hydroxytryptamine efflux in rat brain during a mild, moderate and severe serotonin-toxicity syndrome
Serotonin (5-hydroxytryptamine; 5-HT)-toxicity syndrome, an iatrogenic brain disorder induced by excessive efflux of 5-HT, has received much attention because of increasing incidents of serotonergic antidepressants. However, the neural mechanism by which extracellular 5-HT is elevated to a toxic level for the syndrome remains to be determined. The goal of the present study was to test the hypothesis that extracellular 5-HT
Gongliang Zhang; Swapna Krishnamoorthy; Zhiyuan Ma; Nick P. Vukovich; Xupei Huang; Rui Tao
Serotonin release acts on 5HT2 receptors in the dorsomedial medulla oblongata to elicit airway dilation in mice
Serotonin (5-hydroxytryptamine; 5-HT) excites neurons in the hypoglossal and solitary tract nuclei through 5-hydroxytryptamine\\u000a 2 (5-HT2) receptors, and contributes to genioglossal muscle activation, hypotension and bradycardia. This study investigated\\u000a the influence of 5-HT2 receptor-mediated 5-HT action in the hypoglossal and solitary tract nuclei on respiratory variables,\\u000a particularly airway resistance. Adult male mice were subjected to microdialysis and placed in a
Mitsuko Kanamaru; Ikuo Homma
5-Hydroxytryptamine-induced calcium-channel gating in rainbow trout (Oncorhynchus mykiss) peripheral blood lymphocytes.
The present study was conducted on peripheral blood lympho-cytes of rainbow trout (Oncorhynchus mykiss) to assess the role of 5-hydroxytryptamine (5-HT; 'serotonin') in calcium signalling. 5-HT-induced increases in intracellular free calcium concentrations, [Ca2+]i, and its action was mediated by 5-HT receptor subtype 3 (5-HT3), but not by 5-HT receptor subtype 1A (5-HT1A) or subtype 2 (5-HT2) in these cells. In Ca2+-containing medium (1 mM CaCl2), 5-HT and 2-methyl-5-HT (5-HT3 receptor agonist) induced increases in [Ca2+]i, whereas in Ca2+-free medium (0 Ca2+, 1 mM EGTA), these two agents failed to evoke increases in [Ca2+]i in these cells, demonstrating that 5-HT mobilizes Ca2+ from the extracellular environment. Furthermore, 5-HT-induced increases in [Ca2+]i are not contributed to by the intracellular endoplasmic reticulum (ER) pool, as thapsigargin, an agent that recruits Ca2+ from ER stores, had additive effects on 5-HT-induced [Ca2+]i responses in fish peripheral lymphocytes. 5-HT-induced increases in [Ca2+]i were mediated by 5-HT3 receptors via gating the calcium through L-type, but not N-type, calcium channels in trout lymphocytes.
Ferriere, F; Khan, N A; Meyniel, J P; Deschaux, P
Serotonin 5HT 2C Receptor Signal Transduction
\\u000a The neurotransmitter serotonin (or 5-hydroxytryptamine (5-HT)) binds to at least 14 structurally and pharmacologically distinct\\u000a receptor subtypes. All 5-HT receptors with the exception of 5-HT3 receptor, which is a ligand-gated ion channel, belong to the seven- transmembrane domain G-protein-coupled receptor (GPCR)\\u000a superfamily. Among all of 5-HT receptor subtypes, 5-HT2C receptor raises particular interest because of its important physiological roles in
Maria N. Garnovskaya; John R. Raymond
5-HT1A receptor as a key player in the brain 5-HT system.
Among an impressive variety of identified serotonin receptors, 5-HT1A attracts particular attention due to its central role in the regulation of 5-HT-ergic neurotransmission and the data on its involvement in the mechanisms of stress response, aggressive behavior, anxiety, and depression. This review concentrates on the cross-regulation between 5-HT receptors and the implication of the 5-HT1A receptor in the genetic control of 5-HT-related behavior. Specifically, it describes the (1) functional interactions between 5-HT1A, 5-HT2A, 5-HT3, and 5-HT7 receptors; (2) cross-talk between 5-HT1A receptor and genes encoding key members of the brain 5-HT system; (3) implication of the 5-HT1A receptor in natural hibernation and genetic predisposition to different kinds of defensive behavior; and (4) role of 5-HT1A autoreceptors and heteroreceptors in anxiety, depression, and suicide, and in the antidepressant effect of serotonin reuptake inhibitors. This review provides converging lines of evidence that the 5-HT1A receptor contributes to the action of other 5-HT receptors, modulating their effect on behavior, and describes new data on the unique role of the 5-HT1A receptor in the indirect regulation of gene expression and in the autoregulation of the brain 5-HT system. PMID:23492554
Popova, Nina K; Naumenko, Vladimir S
The 5-HT{sub 2A} serotoninergic receptor is expressed in the MCF-7 human breast cancer cell line and reveals a mitogenic effect of serotonin
Serotonin (5-hydroxytryptamine, 5-HT) has been described as a mitogen in a variety of cell types and carcinomas. It exerts its mitogenic effect by interacting with a wide range of 5-HT receptor types. Certain studies suggest that some selective serotonin re-uptake inhibitors promote breast cancer in animals and humans. This study attempts to clarify the role of serotonin in promoting the growth of neoplastic mammary cells. Expression of the 5-HT{sub 2A} serotoninergic receptor subtype in MCF-7 cells was determined by RT-PCR, Western blotting, and immunofluorescence analysis. The mitogenic effect of 5-HT on MCF-7 cells was determined by means of the MTT proliferation assay. We have demonstrated that the 5-HT{sub 2A} receptor subtype is fully expressed in the MCF-7 human breast cancer cell line, in terms of encoding mRNA and receptor protein. Automated sequencing has confirmed that the 5-HT{sub 2A} receptor present in this cell line is identical to the 5-HT{sub 2A} receptor found in human platelets and in human cerebral cortex. Furthermore, this receptor was found by immunofluorescence to be on the plasma membrane. MTT proliferation assays revealed that 5-HT and DOI, a selective 5-HT{sub 2A} receptor subtype agonist, stimulated MCF-7 cell. These results indicate that 5-HT plays a mitogenic role in neoplastic mammary cells. Our data also indicate that 5-HT exerts this positive growth effect on MCF-7 cells through, in part, the 5-HT{sub 2A} receptor subtype, which is fully expressed in this cell line.
Sonier, Brigitte [Department of Chemistry and Biochemistry, Universite de Moncton, Moncton, NB (Canada); Arseneault, Madeleine [Department of Chemistry and Biochemistry, Universite de Moncton, Moncton, NB (Canada); Institut National de la Recherche Scientifique-Institut Armand-Frappier, Montreal, Que. (Canada); Lavigne, Carole [Department of Biology, Universite de Moncton, Moncton, NB (Canada); Ouellette, Rodney J. [Beausejour Medical Research Institute, Moncton, NB (Canada); Vaillancourt, Cathy [Department of Chemistry and Biochemistry, Universite de Moncton, Moncton, NB (Canada) and Institut National de la Recherche Scientifique-Institut Armand-Frappier, Montreal, Que. (Canada)]. E-mail: email@example.com
Handling of 5-hydroxytryptamine by platelets in migraine.
There is little dispute that a link exists between 5-hydroxytryptamine (5HT) and migraine but the exact mechanism of an attack has yet to be established. The handling of 5HT by the platelet is regarded as a simple model of the handling of 5HT by nerve terminals. If differences are seen in how the platelets from migraineurs handle 5HT compared to those from a control population, it is possible that a similar difference exists in the nerve terminal. The Haemostatometer allows the rapid and simultaneous in vitro assessment of platelet function (shear-induced haemostasis), coagulation and thrombolysis from non anticoagulated blood samples. In this study, a baseline comparison of haemostasis was made on 20 migraineurs between attacks and 20 controls. No differences were found in the results from each of the two groups. 5 microM of 5HT was then added to blood taken from 10 migraineurs and 10 controls and the recordings were repeated. Again, no differences were found between the results from the two groups. In blood taken from both migraineurs and controls, the effect of 5HT was to significantly enhance clotting time and clot lysis. No effect was seen on primary aggregation. The possible reasons for and significance of these findings is discussed. PMID:1399553
MacGregor, E A; Bird, N; Ranson, R; Ridler, C; Wilkinson, M I
The effects of 5?HT on cholinergic contraction in human airways in vitro
Inhaled 5-hydroxytryptamine (5-HT) causes bronchoconstriction in asthmatics, and 5-HT plasma levels are elevated in asthma. Electrical field stimulation (EFS) of human airways, in vitro, evokes cholinergic contraction mediated by the release of acetylcholine (Ach) from postganglionic cholinergic nerves. The present study investigates whether selective 5-HT agonists and antagonists can modulate EFS- induced cholinergic contraction in human airways in vitro. Human
L. j. Dupont; J. l. Pype; M. g. Demedts; P. De Leyn; G. Deneffe; G. m. Verleden
The 5-hydroxytryptamine content of the placenta and foetus during pregnancy in mice
5-Hydroxytryptamine (5HT) levels were measured in blood and tissues from pregnant mice. Blood levels remained constant during pregnancy and were the same as those in nonpregnant female mice. Placental levels of 5HT increased throughout pregnancy as did the foetal levels. The maternal blood volume of the placenta also increased with advancing gestation. 5HT levels were measured after treatment of the mother with 5HT, and the critical placental level of 5HT observed at about the time of death of the foetus was determined. The levels of 5HT in the placenta and foetus after treatment of the mother with several monoamine oxidase inhibitors were measured, and found to show no significant increase above the normal levels in these tissues. Treatment with cyproheptadine, a 5HT antagonist, did not delay parturition.
Robson, J. M.; Senior, Judith B.
Enhancement of 5-hydroxytryptamine-induced behavioral effects following chronic administration of antidepressant drugs.
It has been shown recently that chronic administration of tricyclic antidepressant drugs results in enhanced responsiveness of neurones to iontophoretically applied 5-hydroxytryptamine (5-HT) in rat forebrain regions. The present investigation tested whether this efect is accompanied by an enhancement of behavioral effects of the amine. Behavioral signs of sleep in young chicks following systemic administration of 5-HT were used as an index of the acion of the amine at central receptor sites. Imipramine, desipramine, amitryptiline, pizotifen, and mianserin given 30 min before 5-HT all reduced the duration of 5-HT-induced behavioral depression. However, 6-8 day pretreatment with the same drugs resulted in an increased duration of the 5-HT-induced depression. The results suggest that the antidepressant drugs can block 5-HT receptors in the central nervous system (CNS) and that chronic blockade resulting from repeated administration of the drugs results in an increase in number or sensitivity of 5-HT receptors. PMID:6774372
Jones, R S
5-Hydroxytryptamine-interacting drugs in animal models of anxiety disorders: More than 30 years of research
An overview of the behavioral data arising from the vast literature concerning the involvement of 5-hydroxytryptamine (5-HT) neurotransmission in the regulation of anxiety is presented. More than 1300 experiments were carried out in this area and they provide evidence that: (1) results obtained in ethologically based animal models of anxiety with drugs stimulating 5-HT transmission are most consistent with the
Guy Griebel
Red wine-induced release of [14C]5-hydroxytryptamine from platelets of migraine patients and controls.
Red wine-induced release of [14C]5-hydroxytryptamine (5HT) from platelets of red wine-sensitive migraine patients, migraine patients not sensitive to red wine and controls, was determined in vitro. No significant differences in platelet [14C]5HT release were found between any of the groups investigated. PMID:8825698
Jarman, J; Pattichis, K; Peatfield, R; Glover, V; Sandler, M
Red Wine-Induced Release of [14C]5Hydroxytryptamine from Platelets of Migraine Patients and Controls
Red wine-induced release of [14C]5-hydroxytryptamine (5HT) from platelets of red wine-sensitive migraine patients, migraine patients not sensitive to red wine and controls, was determined in vitro. No significant differences in platelet [14C]5HT release were found between any of the groups investigated.
J Jarman; K Pattichis; R Peatfield; V Glover; M Sandler
Voltammetric detection of 5-hydroxytryptamine release in the rat brain.
5-Hydroxytryptamine (5-HT) is an important molecule in the brain that is implicated in mood and emotional processes. In vivo, its dynamic release and uptake kinetics are poorly understood due to a lack of analytical techniques for its rapid measurement. Whereas fast-scan cyclic voltammetry with carbon fiber microelectrodes is used frequently to monitor subsecond dopamine release in freely moving and anesthetized rats, the electrooxidation of 5-HT forms products that quickly polymerize and irreversibly coat the carbon electrode surface. Previously described modifications of the electrochemical waveform allow stable and sensitive 5-HT measurements in mammalian tissue slice preparations and in the brain of fruit fly larvae. For in vivo applications in mammals, however, the problem of electrode deterioration persists. We identify the root of this problem to be fouling by extracellular metabolites such as 5-hydoxyindole acetic acid (5-HIAA), which is present in 200-1000 times the concentration of 5-HT and displays similar electrochemical properties, including filming of the electrode surface. To impede access of the 5-HIAA to the electrode surface, a thin layer of Nafion, a cation exchange polymer, has been electrodeposited onto cylindrical carbon-fiber microelectrodes. The presence of the Nafion film was confirmed with environmental scanning electron microscopy and was demonstrated by the diminution of the voltammetric signals for 5-HIAA as well as other common anionic species. The modified microelectrodes also display increased sensitivity to 5-HT, yielding a characteristic cyclic voltammogram that is easily distinguishable from other common electroactive brain species. The thickness of the Nafion coating and a diffusion coefficient (D) in the film for 5-HT were evaluated by measuring permeation through Nafion. In vivo, we used physiological, anatomical, and pharmacological evidence to validate the signal as 5-HT. Using Nafion-modified microelectrodes, we present the first endogenous recording of 5-HT in the mammalian brain. PMID:19827792
Hashemi, Parastoo; Dankoski, Elyse C; Petrovic, Jelena; Keithley, Richard B; Wightman, R M
Multiple Microvascular and Astroglial 5Hydroxytryptamine Receptor Subtypes in Human Brain: Molecular and Pharmacologic Characterization
Physiologic and anatomic evidence suggest that 5-hydroxytryptamine (5-HT) neurons regulate local cerebral blood flow and blood-brain barrier permeability. To evaluate the possibility that some of these effects occur directly on the blood vessels, molecular and\\/or pharmacologic approaches were used to assess the presence of 5-HT receptors in human brain microvascular fractions, endothelial and smooth muscle cell cultures, as well as
Zvi Cohen; Isabelle Bouchelet; Jean-Guy Villemure; Rita Ball; Danica B. Stanimirovic; Edith Hamel
Tianeptine: 5HT uptake sites and 5HT 1¢7 receptors modulate memory formation in an autoshaping Pavlovian\\/instrumental task
Recent studies using invertebrate and mammal species have revealed that, endogenous serotonin (5-hydroxytryptamine, 5-HT) modulates cognitive processes, particularly learning and memory, though, at present, it is unclear the manner, where, and how long 5-HT systems are involved. Hence in this work, an attempt was made to study the effects of 5-HT endogenous on memory formation, using a 5-HT uptake facilitator
Alfredo Meneses
Effects of 5-HT2B, 5-HT3 and 5-HT4 receptor antagonists on gastrointestinal motor activity in dogs
AIM: To study the effects of 5-hydroxytryptamine (5-HT) receptor antagonists on normal colonic motor activity in conscious dogs. METHODS: Colonic motor activity was recorded using a strain gauge force transducer in 5 dogs before and after 5-HT2B, 5-HT3 and 5-HT4 receptor antagonist administration. The force transducers were implanted on the serosal surfaces of the gastric antrum, terminal ileum, ileocecal sphincter and colon. Test materials or vehicle alone was administered as an intravenous bolus injection during a quiescent period of the whole colon in the interdigestive state. The effects of these receptor antagonists on normal gastrointestinal motor activity were analyzed. RESULTS: 5-HT2B, 5-HT3 and 5-HT4 receptor antagonists had no contractile effect on the fasting canine terminal ileum. The 5-HT3 and 5-HT4 receptor antagonists inhibited phase III of the interdigestive motor complex of the antrum and significantly inhibited colonic motor activity. In the proximal colon, the inhibitory effect was dose dependent. Dose dependency, however, was not observed in the distal colon. The 5-HT2B receptor antagonist had no contractile effect on normal colonic motor activity. CONCLUSION: The 5-HT3 and 5-HT4 receptor antagonists inhibited normal colonic motor activity. The 5-HT2B receptor antagonist had no contractile effect on normal colonic motor activity.
Morita, Hiroki; Mochiki, Erito; Takahashi, Nobuyuki; Kawamura, Kiyoshi; Watanabe, Akira; Sutou, Toshinaga; Ogawa, Atsushi; Yanai, Mitsuhiro; Ogata, Kyoichi; Fujii, Takaaki; Ohno, Tetsuro; Tsutsumi, Souichi; Asao, Takayuki; Kuwano, Hiroyuki
5-hydroxytryptamine release from platelets by different red wines: implications for migraine
We have confirmed our earlier finding that most red wines are able to bring about 5-hydroxytryptamine (5-HT, serotonin) release from platelets in vitro. Platelets from individual subjects manifested varying degrees of releasing ability but responded to different wines with a similar rank ordering. There was a high correlation (r = 0.87) between the effect of red wine and that of
Katerina Pattichis; Louis L. Louca; Joan Jarman; Merton Sandler; Vivette Glover
The effect of mosapride (5HT4 receptor agonist) on insulin sensitivity and GLUT4 translocation
AimsWe investigated the effect of mosapride, 5HT-4 (5-hydroxytryptamine) agonist, on blood glucose level and insulin sensitivity in subjects with impaired glucose tolerance (IGT) and conducted an in vitro study to evaluate the action mechanism.
J. S. Nam; J. Y. Nam; J. S. Yoo; M. Cho; J. S. Park; C. W. Ahn; B. S. Cha; E. J. Lee; S. K. Lim; K. R. Kim; H. C. Lee
Allosteric modulation of the 5-HT3 receptor
5-Hydroxytryptamine type 3 (5-HT3) receptors are ligand-gated ion channels that play important roles in depression, anxiety, substance abuse, emesis, inflammatory pain, spinal nociception, gastrointestinal function, and cardiovascular reflexes. Probably the most studied modulators of 5-HT3 receptors are the high affinity competitive æsetronÆ antagonists typified by ondansetron. However, there exists a broad range of compounds that modulate the 5-HT3 receptor, not through the orthosteric site but by binding to allosteric sites. Most notable are therapeutic compounds ascribed to certain targets but that allosterically modulate 5-HT3 receptors at clinically relevant concentrations.
Davies, Paul Andrew
Peroxisome proliferator-activated receptor-? ameliorates pulmonary arterial hypertension by inhibiting 5-hydroxytryptamine 2B receptor.
An elevated plasma level of 5-hydroxytryptamine (5-HT) or upregulation of 5-HT receptor signaling or both is implicated in vascular contraction and remodeling in pulmonary arterial hypertension (PAH). Recently, peroxisome proliferator-activated receptor-? (PPAR?) agonists have been shown to ameliorate PAH. However, their effects on the 5-HT-induced contraction of pulmonary arteries remain unknown. Here, we examined the role of PPAR? in inhibiting 5-HT2B receptor (5-HT2BR) to ameliorate PAH. Pulmonary arteries from PAH rats induced by monocrotaline or chronic hypoxia showed an enhanced vasoconstriction in response to BW723C86, a specific agonist for 5-HT2BR. Expression of 5-HT2BR was also increased in pulmonary arteries from the PAH rats, accompanied by vascular remodeling and right ventricular hypertrophy. Treatment with the PPAR? agonist rosiglitazone in vivo reversed the expression and the vasocontractive effect of 5-HT2BR as well as the thickening of pulmonary arteries. In pulmonary artery smooth muscle cells, 5-HT induced the gene expression of 5-HT2BR, which was inhibited by rosiglitazone, pioglitazone, or adenovirus-mediated overexpression of constitutively activated PPAR?. The pharmacological effect of PPAR? was through the suppression of the 5-HT-induced activator protein-1 activity. These results demonstrated the beneficial effect of PPAR? on 5-HT2BR-mediated vasocontraction, providing a new mechanism for the potential use of PPAR? agonists in PAH. PMID:23108648
Liu, Yahan; Tian, Xiao Yu; Mao, Guangmei; Fang, Xi; Fung, Man Lung; Shyy, John Y-J; Huang, Yu; Wang, Nanping
Characterization of the 5-hydroxytryptamine receptors mediating contraction in the pig isolated intravesical ureter
This study was designed to investigate the effect of 5-hydroxytryptamine (5-HT) and to characterize the 5-HT receptors involved in 5-HT responses in the pig intravesical ureter. 5-HT (0.01¢10 ?M) concentration-dependently increased the tone of intravesical ureteral strips, whereas the increases in phasic contractions were concentration-independent. The 5-HT2 receptor agonist ?-methyl 5-HT, mimicked the effect on tone whereas weak or no response was obtained with 5-CT, 8-OH-DPAT, m-chlorophenylbiguanide and RS 67333, 5-HT1, 5-HT1A, 5-HT3 and 5-HT4 receptor agonists, respectively. 5-HT did not induce relaxation of U46619-contracted ureteral preparations. Pargyline (100 ?M), a monoaminooxidase A/B activity inhibitor, produced leftward displacements of the concentration-response curves for 5-HT. 5-HT-induced tone was reduced by the 5-HT2 and 5-HT2A receptor antagonists ritanserine (0.1 ?M) and spiperone (0.2 ?M), respectively. However, 5-HT contraction was not antagonized by cyanopindolol (2 ?M), SDZ¢SER 082 (1 ?M), Y-25130 (1 ?M) and GR 113808 (0.1 ?M), which are respectively, 5-HT1A/1B, 5-HT2B/2C, 5-HT3, and 5-HT4 selective receptor antagonists. Removal of the urothelium did not modify 5-HT-induced contractions. Blockade of neuronal voltage-activated sodium channels, ?-adrenergic receptors and adrenergic neurotransmission with tetrodotoxin (1 ?M), phentolamine (0.3 ?M) and guanethidine (10 ?M), respectively, reduced the contractions to 5-HT. However, physostigmine (1 ?M), atropine (0.1 ?M) and suramin (30 ?M), inhibitors of cholinesterase activity, muscarinic- and purinergic P2-receptors, respectively, failed to modify the contractions to 5-HT. These results suggest that 5-HT increases the tone of the pig intravesical ureter through 5-HT2A receptors located at the smooth muscle. Part of the 5-HT contraction is indirectly mediated via noradrenaline release from sympathetic nerves.
Hernandez, Medardo; Barahona, Maria Victoria; Simonsen, Ulf; Recio, Paz; Rivera, Luis; Martinez, Ana Cristina; Garcia-Sacristan, Albino; Orensanz, Luis M; Prieto, Dolores
Direct Subunit-Dependent Multimodal 5-Hydroxytryptamine3 Receptor Antagonism by Methadone
Homomeric 5-hydroxytryptamine (5-HT)3A and heteromeric 5-HT3AB receptors mediate rapid excitatory responses to serotonin in the central and peripheral nervous systems. The alkaloid morphine, in addition to being a ?-opioid receptor agonist, is a potent competitive inhibitor of 5-HT3 receptors. We examined whether methadone, an opioid often used to treat morphine dependence, also exhibited 5-HT3 receptor antagonist properties. Racemic (R/S)-methadone inhibited currents mediated by human homomeric 5-HT3A receptors (IC50 = 14.1 ▒ 2.5 ?M). Incorporation of the 5-HT3B subunit into heteromeric 5-HT3AB receptors reduced the potency of inhibition by (R/S)-methadone (IC50 = 41.1 ▒ 0.9 ?M). (R/S)-Methadone also increased apparent desensitization of both 5-HT3 receptor subtypes. The inhibition of the 5-HT3A receptor was competitive; however, incorporation of the 5-HT3B subunit caused the appearance of inhibition that was insurmountable by 5-HT. In the absence of rapid desensitization, when dopamine was used as an agonist of 5-HT3AB receptors, the inhibition by (R/S)-methadone was voltage-dependent. The antagonist and desensitization-enhancing effects of (R/S)-methadone were shared by pure (R)- and (S)-methadone enantiomers, which had similar actions on 5-HT-evoked currents mediated by 5-HT3 receptors. However, (R)-methadone exhibited a larger voltage-dependent inhibition of dopamine-evoked currents mediated by 5-HT3AB receptors than did (S)-methadone. Inhibition of 5-HT3A receptors by (R/S)-methadone was not influenced by voltage. Thus, methadone displays multimodal subunit-dependent antagonism of 5-HT3 receptors.
Deeb, Tarek Z.; Sharp, Douglas; Hales, Tim G.
Modulation of 5HT 2A receptor-mediated head-twitch behaviour in the rat by 5HT 2C receptor agonists
The pharmacology of several commonly described 5-hydroxytryptamine (5-HT)2C receptor agonists was investigated in vivo and in vitro at rat 5-HT2A, 5-HT2B, and 5-HT2C receptors. The 5-HT2C receptor agonist, (S)-2-(6-chloro-5-fluoroindol-1-yl)-1-methylethylamine fumarate (Ro 60-0175), did not induce a significant head-twitch response when given alone, yet when administered to rats subsequent to an acute challenge with the selective 5-HT2C receptor antagonist, 6-chloro-5-methyl-1-[6-(2-methylpyridin-3-yloxy) pyridin-3-yl
S. P Vickers; N Easton; C. S Malcolm; N. H Allen; R. H Porter; M. J Bickerdike; G. A Kennett
Interplay between Serotonin 5-HT1A and 5-HT7 Receptors in Depressive Disorders.
Serotonin (5-hydroxytryptamine or 5-HT) is an important neurotransmitter regulating a wide range of physiological and pathological functions via activation of heterogeneously expressed 5-HT receptors. Besides the important role of 5-HT receptors in the pathogenesis of depressive disorders and in their clinical medications, underlying mechanisms are far from being completely understood. This review focuses on possible cross talk between two serotonin receptors, 5-HT1A and the 5-HT7 . Although these receptors are highly co-expressed in brain regions implicated in depression, and most agonists developed for the 5-HT1A or 5-HT7 receptors have cross-reactivity, their functional interaction has not been yet established. It has been recently shown that 5-HT1A and 5-HT7 receptors form homo- and heterodimers both in vitro and in vivo. From the functional point of view, heterodimerization has been shown to play an important role in regulation of receptor-mediated signaling and internalization, suggesting the implication of heterodimerization in the development and maintenance of depression. Interaction between these receptors is also of clinical interest, because both receptors represent an important pharmacological target for the treatment of depression and anxiety. PMID:24935787
Naumenko, Vladimir S; Popova, Nina K; Lacivita, Enza; Leopoldo, Marcello; Ponimaskin, Evgeni G
Memory formation and memory alterations: 5-HT6 and 5-HT7 receptors, novel alternative.
Abstract Agonists and antagonists of the 5-hydroxytryptamine (serotonin) receptor6 (5-HT6) or receptor7 (5-HT7) might improve memory and/or reverse amnesia, although the mechanisms involved are poorly understood. Hence, the current work summarizes recent reviews and findings involving these receptors. Evidence indicates that diverse 5-HT6 receptor antagonists produce promnesic and/or antiamnesic effect in conditions, such as memory formation, age-related cognitive impairments and memory deficit in preclinical studies, as well as in diseases such as schizophrenia, Parkinson's, and Alzheimer's disease (AD). Memory, aging, and AD modify 5-HT6 receptors and signaling cascades; likewise, the modulation of 5-HT6 drugs on memory seems to be accompanied with neural changes. Moreover, 5-HT7 receptors are localized in brain areas mediating memory, including the cortex, hippocampus (e.g., Zola-Morgan and Squire, 1993) and raphe nuclei; however, the role of these receptors on memory has yet to be fully explored. Hence, findings and reviews are summarized in this work. Evidence suggests that both 5-HT7 receptor agonists and antagonists might have promnesic and anti-amnesic effects. These effects seem to be dependent on the basal level of performance, i.e., normal or impaired. Available evidence suggests that a potential utility of 5-HT6 and 5-HT7 receptor in mild-to-moderate AD patients and other memory dysfunctions as therapeutic targets. PMID:24698823
Meneses, Alfredo
No hypothermic response to serotonin in 5HT7 receptor knockout mice
With data from recently available selective antagonists for the 5-HT7 receptor, it has been hypothesized that 5-hydroxytryptamine (5-HT)-induced hypothermia is mediated by the 5-HT7 receptor, an effect previously attributed to other receptor subtypes. It has been established that the biologically active lipid oleamide allosterically interacts with the 5-HT7 receptor to regulate its transmission. The most well characterized effects of oleamide
P. B. Hedlund; P. E. Danielson; E. A. Thomas; K. Slanina; M. J. Carson; J. G. Sutcliffe
Cortical 5HT2A Receptor Signaling Modulates Anxiety-Like Behaviors in Mice
Serotonin [5-hydroxytryptamine (5-HT)] neurotransmission in the central nervous system modulates depression and anxiety-related behaviors in humans and rodents, but the responsible downstream receptors remain poorly understood. We demonstrate that global disruption of 5-HT2A receptor (5HT2AR) signaling in mice reduces inhibition in conflict anxiety paradigms without affecting fear-conditioned and depression-related behaviors. Selective restoration of 5HT2AR signaling to the cortex normalized conflict
Noelia V. Weisstaub; Mingming Zhou; Alena Lira; Evelyn Lambe; Javier Gonzßlez-Maeso; Jean-Pierre Hornung; Etienne Sibille; Mark Underwood; Shigeyoshi Itohara; William T. Dauer; Mark S. Ansorge; Emanuela Morelli; J. John Mann; Miklos Toth; George Aghajanian; Stuart C. Sealfon; Renķ Hen; Jay A. Gingrich
5HT1C receptor-mediated stimulation of inositol phosphate production in pig choroid plexus
1) 5-HT (5-hydroxytryptamine, serotonin) induces inositol phosphate production in a pig choroid plexus preparation. This effect has been pharmacologically characterized and the data compared to those obtained from radioligand binding studies performed with [3H]mesulergine to 5-HT1C sites in pig choroid plexus membranes. 2) The rank order of potency of agonists stimulating inositol phosphate production was: a-methyl-5-HT > 1-methyl-5-HT > DOI
Daniel Hoyer; Christian Waeber; Philippe Schoeffter; Jose Maria Palacios; Anant Dravid
Raised 5-hydroxytryptamine concentrations in enterochromaffin cells in adult coeliac disease.
We measured cytofluorometrically the concentration of 5-hydroxytryptamine (5-HT, serotonin) of individual enterochromaffin (EC) cells in adult coeliac and non-coeliac small intestinal mucosa. The distributions of 5-HT concentration within populations of EC cells in control and coeliac mucosae were log normal and thus contained one single population of EC cells. The median 5-HT concentration per EC cell, and the number of EC cells both increased in coeliac disease, but showed signs of normalisation when gluten was withdrawn from the diet. The results indicate that, besides inducing EC cell hyperplasia, gluten is capable of producing reversible changes in functions of EC cells in adult coeliac disease. PMID:6841643
Enerbõck, L; Hallert, C; Norrby, K
RNA editing of the human serotonin 5-hydroxytryptamine 2C receptor silences constitutive activity.
RNA transcripts encoding the serotonin 5-hydroxytryptamine 2C (5-HT2C) receptor (5-HT2CR) undergo adenosine-to-inosine RNA editing events at up to five specific sites. Compared with rat brain, human brain samples expressed higher levels of RNA transcripts encoding the amino acids valine-serine-valine (5-HT2C-VSV) and valine-glycine-valine (5-HT2C-VGV) at positions 156, 158, and 160, respectively. Agonist stimulation of the nonedited human receptor (5-HT2C-INI) and the edited 5-HT2C-VSV and 5-HT2C-VGV receptor variants stably expressed in NIH-3T3 fibroblasts demonstrated that serotonergic agonists were less potent at the edited receptors. Competition binding experiments revealed a guanine nucleotide-sensitive serotonin high affinity state only for the 5-HT2C-INI receptor; the loss of high affinity agonist binding to the edited receptor demonstrates that RNA editing generates unique 5-HT2CRs that couple less efficiently to G proteins. This reduced G protein coupling for the edited isoforms is primarily due to silencing of the constitutive activity of the nonedited 5-HT2CR. The distinctions in agonist potency and constitutive activity suggest that different edited 5-HT2CRs exhibit distinct responses to serotonergic ligands and further imply that RNA editing represents a novel mechanism for controlling physiological signaling at serotonergic synapses. PMID:10092629
Niswender, C M; Copeland, S C; Herrick-Davis, K; Emeson, R B; Sanders-Bush, E
Effects of the 5HT 7 receptor antagonists SB269970 and DR 4004 in autoshaping Pavlovian\\/instrumental learning task
There is an important debate regarding the functional role of the 5-HT1A and 5-HT7 receptor in memory systems. Hence, the objective of this paper is to investigate the function of serotonin (5-hydroxytryptamine, 5-HT) in memory consolidation, utilising an autoshaping Pavlovian\\/instrumental learning test. Specific antagonists at 5-HT1A (WAY 100635) and 5-HT7 (SB-269970 or DR 4004) receptors administered i.p. or s.c.) after
Alfredo Meneses
Receptors mediating the actions of 5-hydroxytryptamine on the isolated retractor muscle of the penis preparations from Archachatina marginata (Swainson).
1. The effects of some 5-hydroxytryptamine (5-HT) receptor agonist and antagonists on the isolated retractor muscle of the penis of Archachatina marginata were investigated. 2. Both 5-hydroxytryptamine and lysergic acid diethylamide (LSD) contracted the preparations. The mean pD2 values obtained for 5-HT and LSD were 5.26 +/- 0.21 (N = 10) and 6.3 +/- 0.36 (N = 8) respectively. 3. 5-Methoxy, N,N,-dimethyltryptamine (5-MeODMT; N = 6) trifluoromethylphenylpiperazine (TFMPP; N = 6) alpha-methyl 5-hydroxytryptamine (alpha-Me-5-HT); N = 6) and both L and DL-5-hydroxytryptophan (L-5-HTP; N = 6, DL-5-HTP; N = 6) did not contract the preparations even when concentrations up to 10(-4) M were administered. 4. Ketanserin (10(-8)-10(-6) M) produced rightward shift of the concentration-response curve of 5-HT. (pA2 = 8.0 +/- 0.25, slope = 0.34 +/- 0.03; N = 6). 5. The contractions of the RMP to 5-HT were not antagonised by either LY53857 or ICS 205-930. 6. The present study does not reveal the presence of 5-HT1-like or 5HT2 receptors on the RMP. However 5-HT3 receptors do not seem to exist on this invertebrate smooth muscle. PMID:1354106
Innocent, O; Olufemi, A
Effect of 5-hydroxytryptamine and its antagonists on colonic smooth muscle of the rabbit.
The effect of 5-hydroxytryptamine (5HT) was studied in circular and longitudinal muscle from the proximal and distal colon of New Zealand white rabbits. 5HT stimulated a dose-dependent isometric contraction of distal and proximal circular muscle that was greater than in distal longitudinal muscle (P less than 0.01). 5HT did not stimulate taenia coli longitudinal muscle. The EC50 for 5HT stimulation of distal circular muscle (-7.0 +/- 0.1), distal longitudinal muscle, and proximal circular muscle was similar. Methysergide dose-dependently inhibited the 5HT stimulation of both proximal and distal circular muscle. The IC50 for methysergide inhibition of 5HT (5 x 10(-7) M) stimulation was -5.5 +/- 0.2. Ketanserine and ICS 205-930 did not inhibit 5HT stimulation of colonic muscle. Tetrodotoxin (TTX) decreased the potency, but not the efficacy of 5HT stimulation of proximal and distal circular muscle. Atropine decreased the potency (EC50 = -6.6 +/- 0.1) (P less than 0.05) and the efficacy by 40%. Electrical field stimulation (EFS) caused an on-contraction and off-contraction of distal circular muscle and an on-contraction of proximal circular muscle. 5HT decreased the off-contraction of the distal circular muscle but did not affect the on-contraction of the other muscle strips. 5HT receptor antagonists did not affect EFS of the tissue. The studies suggest: (1) 5HT stimulates circular colonic muscle with greater efficacy than longitudinal muscle, (2) 5HT stimulates circular muscle through a 5HT1 receptor, (3) there is atropine-sensitive and atropine-insensitive 5HT stimulation of circular colonic muscle, (4) 5HT inhibits neurons responsible for the off-contraction in distal circular muscle without affecting the on-contraction.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1988260
Ng, W W; Jing, J; Hyman, P E; Snape, W J
Gamma-mangostin, a novel type of 5-hydroxytryptamine 2A receptor antagonist.
Gamma-mangostin, purified from the fruit hull of the medicinal plant Garcinia mangostana caused a parallel rightwards shift of the concentration/response curve for the contraction elicited by 5-hydroxytryptamine (5-HT) in the rabbit aorta (pA2 = 8.2) without affecting the contractile responses to KCl, phenylephrine (alpha1) or histamine (H1). The perfusion pressure response of rat coronary artery to 5-HT (5-HT2A) was reduced concentration dependently by gamma-mangostin (IC50 = 0.32 microM). 5-HT amplified, ADP-induced aggregation of rabbit platelets (5-HT2A) was inhibited by gamma-mangostin (IC50 = 0.29 microM), whereas that induced by thrombin was not affected, nor did gamma-mangostin affect 5-HT-induced contraction of the guinea-pig ileum (5-HT3)in the presence of 5-HT1, 5-HT2 and 5-HT4 receptor antagonists. Furthermore, 5-HT-induced contraction of the rat fundus (5-HT2B) and 5-HT-induced relaxation of the rabbit aorta in the presence of ketanserin (5-HT1) and carbachol-induced contraction of the guinea-pig ileum (muscarinic M3) were not affected by gamma-mangostin (5 microM). Gamma-mangostin inhibited [3H]spiperone binding to cultured rat aortic myocytes (IC50 = 3.5 nM). The Kd for [3H]spiperone binding was increased by gamma-mangostin (3 nM) from 11.7 to 27.4 nM without affecting Bmax. These results suggest that gamma-mangostin is a novel competitive antagonist, free from a nitrogen atom, for the 5-HT2A receptors in vascular smooth muscles and platelets. PMID:9459569
Chairungsrilerd, N; Furukawa, K I; Ohta, T; Nozoe, S; Ohizumi, Y
Long-term effect of lithium on the uptake of 5-hydroxytryptamine by human platelets.
1 The content, uptake and storage of 5-hydroxytryptamine (5-HT) in platelets were determined in eight manic-depressive patients not on lithium (Li); in ten manic-depressive patients on Li; and in ten apparently normal persons as controls. 2 Platelets from the patients, whether or not on Li, contained less 5-HT than platelets from normal people. 3 5-HT uptake and storage by platelets from untreated patients were significantly lower than those of control subjects. 4 When patients had been on Li for 3 months or longer the diminished uptake and storage of 5-HT by their platelets were more than fully reversed. 5 Li added to platelet-rich plasma in vitro had no effect on the uptake of 5-HT by platelets.
Born, G V; Grignani, G; Martin, K
Pronociceptive role of peripheral and spinal 5HT 7 receptors in the formalin test
The possible pronociceptive role of peripheral and spinal 5-HT7 receptors in the formalin test was assessed. Local administration of 5-HT7 (SB-269970, 2.5¢77.1nmol\\/paw), but not 5-HT1A (WAY-100635, 1¢60nmol\\/paw), receptor antagonist significantly reduced formalin-induced flinching. Local 5-hydroxytryptamine (5-HT, 3¢100nmol\\/paw) or 5-carboxamidotryptamine (5-CT, 0.3¢3nmol\\/paw) (a 5-HT7\\/1A receptor agonist) augmented, in a dose-dependent manner, 0.5% formalin-induced nociceptive behavior. The local pronociceptive effect of 5-HT
Hķctor I. Rocha-Gonzßlez; Alfredo Meneses; Susan M. Carlton; Vinicio Granados-Soto
Coexpression of 5HT 2A and 5HT 4 receptors coupled to distinct signaling pathways in human intestinal muscle cells
Background & Aims: The type and function of 5-hydroxytryptamine (5-HT) receptors on intestinal muscle cells in humans are not known. 5-HT receptors were characterized pharmacologically and by radioligand binding. Methods: Contraction, relaxation, inositol 1,4,5-triphosphate (IP3) and adenosine 3?,5?-cyclic monophosphate (cAMP) formation, and 5-HT binding were measured in dispersed muscle cells and in cells in which only one receptor type was
John F. Kuemmerle; Karnam S. Murthy; John R. Grider; Daniel C. Martin; Gabriel M. Makhlouf
Radioligand binding analysis of knockout mice reveals 5-hydroxytryptamine 7 receptor distribution and uncovers 8-hydroxy-2-(di- n-propylamino)tetralin interaction with ? 2 adrenergic receptors
In the present autoradiographic study, we took advantage of 5-hydroxytryptamine7 (5-HT7) receptor knockout mice to analyze the brain distribution of 5-HT7 receptor binding sites using [3H]5-carboxamidotryptamine (5-CT; a 5-HT1A\\/1B\\/1D\\/5\\/7 receptor ligand) and [3H]8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; a 5-HT1A\\/7 receptor ligand). Low to moderate densities of [3H]5-CT (2ĀnM) binding sites insensitive to pindolol (10Ā?M, for 5-HT1A\\/1B receptor blockade) and GR-127935 (1Ā?M; for 5-HT1D
P Bonaventure; D Nepomuceno; L Hein; J. G Sutcliffe; T Lovenberg; P. B Hedlund
Evidence for the presynaptic action of 5-hydroxytryptamine and the involvement of purinergic innervation in the rabbit lower urinary tract.
1. The effects of 5-hydroxytryptamine (5-HT) were studied in vitro on bladder and urethral muscle strips from the rabbit. 5-HT produced dose-dependent contraction in the detrusor and urethra. 2. The 5-HT-induced contraction could be dose-dependently inhibited by the 5-HT3 antagonists MDL 72222, ICS 205-930 and BRL 43694. No effect of ketanserin, methysergide or metitepine was observed on the contractile response to 5-HT. 3. Atropine and alpha, beta-methylene ATP both partially blocked the contractile response to 5-HT. Together they caused more inhibition than either alone. 4. Atropine and alpha, beta-methylene ATP also inhibited the contractile response to electrical field stimulation. The 5-HT3 antagonist MDL 72222 had no effect on the contraction to field stimulation. 5. The atropine- and alpha, beta-methylene ATP-resistant components of 5-HT-induced contraction were not affected by the 5-HT1 antagonists metitepine, the 5-HT2 antagonists ketanserin and methysergide or the 5-HT3 antagonists MDL 72222, ICS 205-930 and BRL 43694. 6. Tetrodotoxin, hexamethonium, phentolamine and prazosin had no effect on the contractile response to 5-HT. 7. These results suggest that in the rabbit lower urinary tract (i) there are 5-HT3 receptors, (ii) the contractile response to 5-HT is mediated by presynaptic stimulation, (iii) there is non-adrenergic, non-cholinergic excitatory neurotransmission.
Chen, H. I.
Characterization of a novel /sup 3/H-5-hydroxytryptamine binding site subtype in bovine brain membranes
/sup 3/H-5-Hydroxytryptamine (5-HT) binding sites were analyzed in bovine brain membranes. The addition of either the 5-HT1A-selective drug 8-OH-DPAT (100 nM) or the 5-HT1C-selective drug mesulergine (100 nM) to the assay resulted in a 5-10% decrease in specific /sup 3/H-5-HT binding. Scatchard analysis revealed that the simultaneous addition of both drugs decreased the Bmax of /sup 3/H-5-HT binding by 10-15% without affecting the KD value (1.8 +/- 0.3 nM). Competition studies using a series of pharmacologic agents revealed that the sites labeled by /sup 3/H-5-HT in bovine caudate in the presence of 100 nM 8-OH-DPAT and 100 nM mesulergine appear to be homogeneous. 5-HT1A selective agents such as 8-OH-DPAT, ipsapirone, and buspirone display micromolar affinities for these sites. RU 24969 and (-)pindolol are approximately 2 orders of magnitude less potent at these sites than at 5-HT1B sites which have been identified in rat brain. Agents displaying nanomolar potencies for 5-HT1C sites such as mianserin and mesulergine are 2-3 orders of magnitude less potent at the /sup 3/H-5-HT binding sites in bovine caudate. In addition, both 5-HT2- and 5-HT3-selective agents are essentially inactive at these binding sites. These /sup 3/H-5-HT sites display nanomolar affinity for 5-carboxyamidotryptamine, 5-methoxytryptamine, metergoline, and 5-HT. Apparent Ki values of 10-100 nM are obtained for d-LSD, RU 24969, methiothepin, tryptamine, methysergide, and yohimbine, whereas I-LSD and corynanthine are significantly less potent. In addition, these /sup 3/H-5-HT labeled sites are regulated by guanine nucleotides and calcium. Regional studies indicate that this class of sites is most dense in the basal ganglia but exists in all regions of bovine brain. These data therefore demonstrate the presence of a homogeneous class of 5-HT1 binding sites in bovine caudate that is pharmacologically distinct from previously defined 5-HT1A, 5-HT1B, 5-HT1C, 5-HT2, and 5-HT3 receptor subtypes. (Abstract Truncated)
Heuring, R.E.; Peroutka, S.J.
General anesthetic-induced channel gating enhancement of 5-hydroxytryptamine type 3 receptors depends on receptor subunit composition.
5-Hydroxytryptamine (serotonin) (5-HT) type 3 (5-HT(3)) receptors are members of an anesthetic-sensitive superfamily of Cys-loop ligand-gated ion channels that can be formed as homomeric 5-HT(3A) or heteromeric 5-HT(3AB) receptors. When the efficacious agonist 5-HT is used, the inhaled anesthetics halothane and chloroform (at clinically relevant concentrations) significantly reduce the agonist EC(50) for 5-HT(3A) receptors but not for 5-HT(3AB) receptors. In the present study, we used dopamine (DA), a highly inefficacious agonist for 5-HT(3) receptors, to determine whether the difference in sensitivity between 5-HT(3A) and 5-HT(3AB) receptors to the potentiating effects of halothane and chloroform is due to differential modulation of agonist affinity, channel gating, or both. Using the two-electrode voltage-clamp technique with 5-HT(3A) and 5-HT(3AB) receptors expressed in Xenopus oocytes, we found that chloroform and halothane enhanced currents evoked by receptor-saturating concentrations of DA for both receptor subtypes in a concentration-dependent manner but that the magnitude of enhancement was substantially greater for 5-HT(3A) receptors than for 5-HT(3AB) receptors. Isoflurane induced only a small enhancement of currents evoked by receptor-saturating concentrations of DA for 5-HT(3A) receptors and no enhancement for 5-HT(3AB) receptors. For both receptor subtypes, none of the three test anesthetics significantly altered the agonist EC(50) for DA, implying that these anesthetics do not affect agonist binding affinity. Our results show that chloroform, halothane, and (to a much lesser degree) isoflurane enhance channel gating for 5-HT(3A) receptors and that the incorporation of 5-HT(3B) subunits to produce heteromeric 5-HT(3AB) receptors markedly attenuates the ability of these anesthetics to enhance channel gating. PMID:16081679
Solt, Ken; Stevens, Renna J; Davies, Paul A; Raines, Douglas E
Increased expression of 5-hydroxytryptamine2A\\/B receptors in idiopathic pulmonary fibrosis: a rationale for therapeutic intervention
BackgroundIdiopathic pulmonary fibrosis (IPF) has a poor prognosis and limited responsiveness to available treatments. It is characterised by epithelial cell injury, fibroblast activation and proliferation and extracellular matrix deposition. Serotonin (5-hydroxytryptamine; 5-HT) induces fibroblast proliferation via the 5-HTR2A and 5-HTR2B receptors, but its pathophysiological role in IPF remains unclear. A study was undertaken to determine the expression of 5-HT receptors
Melanie K÷nigshoff; Rio Dumitrascu; Sergey Udalov; Oana Veronica Amarie; Rudolf Reiter; Friedrich Grimminger; Werner Seeger; Ralph Theo Schermuly; Oliver Eickelberg
Regional differences in the effects of forced swimming on extracellular levels of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid
The effects of forced swimming for 30 min on extracellular 5-hydroxytryptamine (5-HT) levels were examined in five brain regions in rats using in vivo microdialysis. A single dialysis probe was implanted under surgical anesthesia into either the striatum, ventral hippocampus, frontal cortex, amygdala, or lateral septum on the day before the study. Dialysate content of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA)
Lynn G. Kirby; Angela R. Allen; Irwin Lucki
Ventricles from 50 species of bivalved molluscs were surveyed for their me chanical responses to the molluscan neuropeptide FMRFamide (Phe-Met-Arg-Phe NH2) and to 5-hydroxytryptamine (5HT). Both were predominantly cardioexci tatory, but neither was exclusively so. FMRFamide was inhibitory or weakly cx citatory more often than 5HT, and such effects were most common in the subclasses Paleoheterodonta and Heterodonta. In contrast,
Antidepressant activity: contribution of brain microdialysis in knock-out mice to the understanding of BDNF/5-HT transporter/5-HT autoreceptor interactions
Why antidepressants vary in terms of efficacy is currently unclear. Despite the leadership of selective serotonin reuptake inhibitors (SSRIs) in the treatment of depression, the precise neurobiological mechanisms involved in their therapeutic action are poorly understood. A better knowledge of molecular interactions between monoaminergic system, pre- and post-synaptic partners, brain neuronal circuits and regions involved may help to overcome limitations of current treatments and identify new therapeutic targets. Intracerebral in vivo microdialysis (ICM) already provided important information about the brain mechanism of action of antidepressants first in anesthetized rats in the early 1990s, and since then in conscious wild-type or knock-out mice. The principle of ICM is based on the balance between release of neurotransmitters (e.g., monoamines) and reuptake by selective transporters [e.g., serotonin transporter for serotonin 5-hydroxytryptamine (5-HT)]. Complementary to electrophysiology, this technique reflects pre-synaptic monoamines release and intrasynaptic events corresponding to ?80% of whole brain tissue content. The inhibitory role of serotonergic autoreceptors infers that they limit somatodendritic and nerve terminal 5-HT release. It has been proposed that activation of 5-HT1A and 5-HT1B receptor sub-types limits the antidepressant-like activity of SSRIs. This hypothesis is based partially on results obtained in ICM experiments performed in na've, non-stressed rodents. The present review will first remind the principle and methodology of ICM performed in mice. The crucial need of developing animal models that display anxiety and depression-like behaviors, neurochemical and brain morphological phenotypes reminiscent of these mood disorders in humans, will be underlined. Recently developed genetic mouse models have been generated to independently manipulate 5-HT1A auto and heteroreceptors and ICM helped to clarify the role of the pre-synaptic component, i.e., by measuring extracellular levels of neurotransmitters in serotonergic nerve terminal regions and raphe nuclei. Finally, we will summarize main advantages of using ICM in mice through recent examples obtained in knock-outs (drug infusion through the ICM probe allows the search of a correlation between changes in extracellular neurotransmitter levels and antidepressant-like activity) or alternatives (infusion of a small-interfering RNA suppressing receptor functions in the mouse brain). We will also focus this review on post-synaptic components such as brain-derived neurotrophic factor in adult hippocampus that plays a crucial role in the neurogenic and anxiolytic/antidepressant-like activity of chronic SSRI treatment. Limitations of ICM will also be considered.
Gardier, Alain M.
Characterization of the molecular fragment that is responsible for agonism of pergolide at serotonin 5-Hydroxytryptamine2B and 5-Hydroxytryptamine2A receptors.
Cardiac-valve regurgitation observed in Parkinson patients treated with the ergoline dopamine receptor agonist 8beta-methylthiomethyl-6-propylergoline (pergolide) has been associated with the agonist efficacy of the drug at 5-hydroxytryptamine(2B) (5-HT(2B)) receptors. 5-HT(2A) receptors may also play a role in pergolide-induced cardiac-valve regurgitation. We studied the pharmacological profile of pergolide and eight derivatives in porcine vascular rings endowed with 5-HT(2B) and 5-HT(2A) receptors to detect the molecular fragment of the pergolide molecule that may be responsible for agonism at these receptors. Pergolide derivatives showed a different substitution pattern at N(6), and the side chain at C(8) was modified by replacement of the sulfur against an oxygen atom. We demonstrate that the potent agonism of pergolide both at 5-HT(2B) and 5-HT(2A) receptors is retained when the N(6) propyl substituent is replaced by ethyl. However, agonism can be converted into antagonism if N(6) propyl is replaced by methyl. The N(6)-unsubstituted derivative was a low efficacy 5-HT(2B) receptor partial agonist and a 5-HT(2A) receptor antagonist. This pharmacological pattern was also applicable for pergolide congeners with an oxygen in the side chain at C(8). 6-Methylpergolide retained agonist efficacy and potency compared with pergolide at human (h) D(2LONG(L)) and hD(2SHORT(S)) receptors as determined by guanosine 5'-O-(3-[(35)S]thio)triphosphate binding. Based on the ability of pergolide to produce potent agonism at 5-HT(2B) receptors and the failure of 6-methylpergolide to act as an agonist but as a potent antagonist, we conclude that the N(6) propyl substituent of pergolide is crucial for 5-HT(2B) receptor agonism and thus a determinant of valvular regurgitation. PMID:18096760
G÷rnemann, Tilo; H³bner, Harald; Gmeiner, Peter; Horowski, Reinhard; Lattķ, Klaus Peter; Flieger, Miroslav; Pertz, Heinz H
No association between bipolar affective disorder and a serotonin receptor (5HT2A) polymorphism
The serotonergic system is implicated in the pathogenesis of affective disorders. In particular, the role of the postsynaptic 5-hydroxytryptamine (serotonin) type 2 receptor (5-HT2) has been documented by several studies. The 5-HT2A receptor gene located on chromosome 13 (13q14-21) can be considered a candidate gene for bipolar affective disorder (BPAD). We tested association between a 5-HT2A receptor DNA variant and
Brigitte Mahieu; Daniel Souery; Olivier Lipp; Karin Mendelbaum; Geert Verheyen; Viviane De Maertelaer; Christine Van Broeckhoven; Julien Mendlewicz
5HT 7 receptor-mediated relaxation of the oviduct in nonpregnant proestrus pigs
The effects of 5-hydroxytryptamine (5-HT) on the muscle tonus of the ampulla and isthmus of the oviduct isolated from nonpregnant proestrus pigs were investigated, and the 5-HT receptor subtype and mechanisms of the responses were analyzed. 5-HT (1 nM¢10 ?M) caused a relaxation of longitudinal and circular muscles of the isthmus in a concentration-dependent manner. Tetrodotoxin did not change the
Mayuko Inoue; Takio Kitazawa; Jinshan Cao; Tetsuro Taneike
5HT 7 Receptors as Favorable Pharmacological Targets for Drug Discovery
The 5-hydroxytryptamine7 (5-HT7) receptor was among a group of 5-HT receptors discovered through targeted cloning strategies 13 yr ago. It is a seven-transmembrane-domain\\u000a G protein-coupled receptor positively linked to adenylyl cyclase. The distributions of 5-HT7 receptor mRNA, immunolabeling, and radioligand binding show strong similarities, with the highest densities found in the\\u000a thalamus and hypothalamus, but with significant presence also in
Peter B. Hedlund; J. Gregor Sutcliffe
Expression of the 5HT receptors in rat brain during memory consolidation
Serotonin (5-hydroxytryptamine, 5-HT) system displays more than 14 receptors subtypes on brain areas involved in learning and memory processes, and pharmacological manipulation of specific receptors selectively affects memory formation. In order to begin the search of 5-HT receptors expression during memory formation, in this work, we aimed to determine, by autoradiography (using [3H] 5-HT as ligand, 2nM, specific activity 123Ci\\/mmol),
A Meneses; L Manuel-Apolinar; L Rocha; E Castillo; C Castillo
Naftidrofuryl inhibits the release of 5-hydroxytryptamine and platelet-derived growth factor from human platelets.
Angioplasty and bypass-grafting are associated with restenosis which limits their efficacy. Platelet-rich thrombus formation is the predominant cause of acute occlusion whereas platelet release products with proliferating properties, e.g. 5-hydroxytryptamine (5-HT) and platelet-derived growth factor (PDGF), may contribute to late restenosis. Naftidrofuryl (NAF), a drug for the treatment of peripheral vascular disease, was shown previously to inhibit platelet shape change and aggregation. This study establishes whether NAF inhibits the release of 5-HT and PDGF from platelets obtained from healthy subjects. Platelets stimulated with agonists aggregated less and released less 5-HT/PDGF when pre-incubated with NAF. Indomethacin (INDO), a cyclooxygenase inhibitor, alone inhibited aggregation and PDGF/5-HT release; NAF enhanced the inhibitory effects of INDO. The effect of NAF, on its own or in combination with a cyclooxygenase inhibitor, may therefore confer protection against graft occlusion. PMID:7834867
Barradas, M A; Jagroop, I A; Mikhailidis, D P
Modulatory Role of 5HT3 Receptors in Gastric Function and Ethanol-lnduced Mucosal Damage in Rat Stomachs
The involvement of 5-hydroxytryptamine (5-HT) in gastric function and mucosal damage has been defined. 5-HT also potentiates lesion formation in animals. The current study investigated further whether these actions are mediated through 5-HT3 receptors in rats. Ondansetron, a 5-HT3 receptor antagonist, was given subcutaneously, 2 or 4 mg\\/kg, 30 min before the gastric parameters were measured. The higher dose of
C. H. Cho; M. W. L. Koo; J. K. S. Ko
Desensitization and resensitization of human platelets to 5-hydroxytryptamine at the level of signal transduction.
Desensitization of platelets to 5-hydroxytryptamine (5HT) (1 microM), during active removal of the agonist by the platelet 5HT-uptake system, was studied at the level of signal transduction. Desensitization to 5HT was dose-dependent and homologous. Without occupation of the 5HT2 receptor, neither an increase in cytosolic [Ca2+] (30 nM ionomycin), nor a separate or simultaneous activation of protein kinase C (by 10 microM 1-oleoyl-2-acetylglycerol), could induce desensitization to 5HT (1 microM). During the early phase of desensitization, the 5HT2 receptor was coupled to phospholipase C, whereas during the late phase of desensitization this coupling was disconnected. However, after disappearance of the agonist, the coupling in the resting platelet recovered quickly, and was nearly complete (82%) after 30 min. During this resensitization, the 5HT-inducibility of activation of phospholipase C, of the increase in cytosolic [Ca2+] and of stimulation of protein kinase C were restored in parallel. The time course for resensitization of the 5HT-induced increase in cytosolic [Ca2+] was independent of the presence of extracellular Ca2+. It is concluded that, after dissociation of 5HT from the platelet 5HT2-receptor, 5HT-induced responses rapidly resensitize. Because of its short duration and the parallelism in recovery between the different 'down-stream phospholipase C' intracellular transduction signals, it is considered that desensitization arises from a reversible change in the transduction mechanism at a step up to or including the activation of phospholipase C. Neither desensitization nor resensitization to 5HT is dependent on the presence of extracellular Ca2+. Images Figure 7
Roevens, P; de Chaffoy de Courcelles, D
Allosteric regulation by oleamide of the binding properties of 5-hydroxytryptamine7 receptors.
Oleamide belongs to a family of amidated lipids with diverse biological activities, including sleep induction and signaling modulation of several 5-hydroxytryptamine (5-HT) receptor subtypes, including 5-HT1A, 5-HT2A/2C, and 5-HT7. The 5-HT7 receptor, predominantly localized in the hypothalamus, hippocampus, and frontal cortex, stimulates cyclic AMP formation and is thought to be involved in the regulation of sleep-wake cycles. Recently, it was proposed that oleamide acts at an allosteric site on the 5-HT7 receptor to regulate cyclic AMP formation. We have further investigated the interaction between oleamide and 5-HT7 receptors by performing radioligand binding assays with HeLa cells transfected with the 5-HT7 receptor. Methiothepin, clozapine, and 5-HT all displaced specific [3H]5-HT (100 nM) binding, with pK(D) values of 7.55, 7.85, and 8.39, respectively. Oleamide also displaced [3H]5-HT binding, but the maximum inhibition was only 40% of the binding. Taking allosteric (see below) cooperativity into account, a K(D) of 2.69 nM was calculated for oleamide. In saturation binding experiments, oleamide caused a 3-fold decrease in the affinity of [3H]5-HT for the 5-HT7 receptor, without affecting the number of binding sites. A Schild analysis showed that the induced shift in affinity of [3H]5-HT reached a plateau, unlike that of a competitive inhibitor, illustrating the allosteric nature of the interaction between oleamide and the 5-HT7 receptor. Oleic acid, the product of oleamide hydrolysis, had a similar effect on [3H]5-HT binding, whereas structural analogs of oleamide, trans-9,10-octadecenamide, cis-8,9-octadecenamide, and erucamide, did not alter [3H]5-HT binding significantly. The findings support the hypothesis that oleamide acts via an allosteric site on the 5-HT7 receptor regulating receptor affinity. PMID:10571256
Hedlund, P B; Carson, M J; Sutcliffe, J G; Thomas, E A
Synergism Between a Serotonin 5-HT2A Receptor (5-HT2AR) Antagonist and 5-HT2CR Agonist Suggests New Pharmacotherapeutics for Cocaine Addiction
Relapse to cocaine dependence, even after extended abstinence, involves a number of liability factors including impulsivity (predisposition toward rapid, unplanned reactions to stimuli without regard to negative consequences) and cue reactivity (sensitivity to cues associated with cocaine-taking which can promote cocaine-seeking). These factors have been mechanistically linked to serotonin (5-hydroxytryptamine, 5-HT) signaling through the 5-HT2A receptor (5-HT2AR) and 5-HT2CR; either a selective 5-HT2AR antagonist or a 5-HT2CR agonist suppresses impulsivity and cocaine-seeking in preclinical models. We conducted proof-of-concept analyses to evaluate whether a combination of 5-HT2AR antagonist plus 5-HT2CR agonist would have synergistic effects over these liability factors for relapse as measured in a 1-choice serial reaction time task and cocaine self-administration/reinstatement assay. Combined administration of a dose of the selective 5-HT2AR antagonist M100907 plus the 5-HT2CR agonist WAY163909, each ineffective alone, synergistically suppressed cocaine-induced hyperactivity, inherent and cocaine-evoked impulsive action, as well as cue- and cocaine-primed reinstatement of cocaine-seeking behavior. The identification of synergism between a 5-HT2AR antagonist plus a 5-HT2CR agonist to attenuate these factors important in relapse indicates the promise of a bifunctional ligand as an anti-addiction pharmacotherapeutic, setting the stage to develop new ligands with improved efficacy, potency, selectivity, and in vivo profiles over the individual molecules.
5-HT3 and 5-HT4 antagonists inhibit peristaltic contractions in guinea-pig distal colon by mechanisms independent of endogenous 5-HT
Recent studies have shown that endogenous serotonin is not required for colonic peristalsis in vitro, nor gastrointestinal (GI) transit in vivo. However, antagonists of 5-Hydroxytryptamine (5-HT) receptors can inhibit peristalsis and GI-transit in mammals, including humans. This raises the question of how these antagonists inhibit GI-motility and transit, if depletion of endogenous 5-HT does not cause any significant inhibitory changes to either GI-motility or transit? We investigated the mechanism by which 5-HT3 and 5-HT4 antagonists inhibit distension-evoked peristaltic contractions in guinea-pig distal colon. In control animals, repetitive peristaltic contractions of the circular muscle were evoked in response to fixed fecal pellet distension. Distension-evoked peristaltic contractions were unaffected in animals with mucosa and submucosal plexus removed, that were also treated with reserpine (to deplete neuronal 5-HT). In control animals, peristaltic contractions were blocked temporarily by ondansetron (1¢10 ?M) and SDZ-205¢557 (1¢10 ?M) in many animals. Interestingly, after this temporary blockade, and whilst in the continued presence of these antagonists, peristaltic contractions recovered, with characteristics no different from controls. Surprisingly, similar effects were seen in mucosa-free preparations, which had no detectable 5-HT, as detected by mass spectrometry. In summary, distension-evoked peristaltic reflex contractions of the circular muscle layer of the guinea-pig colon can be inhibited temporarily, or permanently, in the same preparation by selective 5-HT3 and 5-HT4 antagonists, depending on the concentration of the antagonists applied. These effects also occur in preparations that lack any detectable 5-HT. We suggest caution should be exercised when interpreting the effects of 5-HT3 and 5-HT4 antagonists; and the role of endogenous 5-HT, in the generation of distension-evoked colonic peristalsis.
Sia, Tiong C.; Whiting, Malcolm; Kyloh, Melinda; Nicholas, Sarah J.; Oliver, John; Brookes, Simon J.; Dinning, Phil G.; Wattchow, David A.; Spencer, Nick J.
Role of serotonin 5-HT? receptors in intestinal inflammation.
Serotonin (5-hydroxytryptamine; 5-HT), a well-characterized neurotransmitter in the central nervous system, plays a crucial role in regulating mood, body temperature, sleep, appetite, and metabolism. Serotonin is synthesized in the serotonergic neuron of the central nervous system; however, approximately 90% of serotonin is synthesized and localized in the gastrointestinal (GI) tract, especially in the enterochromaffin (EC) cells. In the GI tract, serotonin mediates control over a variety of physiological functions such as contraction/relaxation of smooth muscle, and peristaltic and secretory reflexes, directly or indirectly through intrinsic primary afferent neurons. The receptors mediating the action of serotonin are mainly classified into 7 major groups known as the 5-HT1 to 5-HT7 receptors. The 5-HT3 receptor is distinguished from among the other 5-HT receptor subtypes because it is only a ligand-gated ion channel, whereas the other subtypes serve as G protein-coupled receptors. The 5-HT3 receptor, which is generally considered to be localized in the central and peripheral nervous systems, is involved in processes associated with emotion, cognition, memory, pain perception, and GI functions including secretion and motility. Recently, an increasing number of findings have provided evidence of the important role of the 5-HT3 receptor in the regulation of inflammatory and immune responses. In fact, several 5-HT3 receptor antagonists have been reported to ameliorate intestinal inflammation. Therefore, this review focuses on the role of 5-HT3 receptors in the pathogenesis of intestinal inflammation. PMID:23995650
Kato, Shinichi
Varenicline Is a Potent Agonist of the Human 5-Hydroxytryptamine3 ReceptorS?
Varenicline, a widely used and successful smoking cessation agent, acts as a partial agonist at nicotinic acetylcholine receptors. Here, we explore the effects of varenicline at human and mouse 5-Hydroxytryptamine3 (5-HT3) receptors. Application of varenicline to human 5-HT3 receptors expressed in Xenopus laevis oocytes reveal it is almost a full agonist (Rmax = 80%) with an EC50 (5.9 ?M) 3-fold higher than 5-HT. At mouse 5-HT3 receptors varenicline is a partial agonist (Rmax = 35%) with an EC50 (18 ?M) 20-fold higher than 5-HT. Displacement of the competitive 5-HT3 receptor antagonist [3H]granisetron reveals similar IC50 values for varenicline at mouse and human receptors expressed in human embryonic kidney 293 cells, although studies in these cells using a membrane potential-sensitive dye show that again varenicline is a 4- or 35-fold less potent agonist than 5-HT in human and mouse receptors, respectively. Thus the data suggest that the efficacy, but not the affinity, of varenicline is greater at human 5-HT3 receptors compared with mouse. Docking studies provide a possible explanation for this difference, because they suggest distinct orientations of the ligand in the mouse versus human 5-HT3 agonist binding sites. Additional binding selectivity studies in a broad panel of recombinant receptors and enzymes confirmed an interaction with 5-HT3 receptors but revealed no additional interactions of varenicline. Therefore, activation of human 5-HT3 receptors may be responsible for some of the side effects that preclude use of higher doses during varenicline treatment.
Thompson, A. J.; Bencherif, M.; Lester, H. A.
Varenicline is a potent agonist of the human 5-hydroxytryptamine3 receptor.
Varenicline, a widely used and successful smoking cessation agent, acts as a partial agonist at nicotinic acetylcholine receptors. Here, we explore the effects of varenicline at human and mouse 5-Hydroxytryptamine(3) (5-HT(3)) receptors. Application of varenicline to human 5-HT(3) receptors expressed in Xenopus laevis oocytes reveal it is almost a full agonist (R(max) = 80%) with an EC(50) (5.9 ?M) 3-fold higher than 5-HT. At mouse 5-HT(3) receptors varenicline is a partial agonist (R(max) = 35%) with an EC(50) (18 ?M) 20-fold higher than 5-HT. Displacement of the competitive 5-HT(3) receptor antagonist [(3)H]granisetron reveals similar IC(50) values for varenicline at mouse and human receptors expressed in human embryonic kidney 293 cells, although studies in these cells using a membrane potential-sensitive dye show that again varenicline is a 4- or 35-fold less potent agonist than 5-HT in human and mouse receptors, respectively. Thus the data suggest that the efficacy, but not the affinity, of varenicline is greater at human 5-HT(3) receptors compared with mouse. Docking studies provide a possible explanation for this difference, because they suggest distinct orientations of the ligand in the mouse versus human 5-HT(3) agonist binding sites. Additional binding selectivity studies in a broad panel of recombinant receptors and enzymes confirmed an interaction with 5-HT(3) receptors but revealed no additional interactions of varenicline. Therefore, activation of human 5-HT(3) receptors may be responsible for some of the side effects that preclude use of higher doses during varenicline treatment. PMID:21775477
Lummis, S C R; Thompson, A J; Bencherif, M; Lester, H A
Effects of repeated treatment with fluoxetine and citalopram, 5-HT uptake inhibitors, on 5-HT1A and 5-HT2 receptors in the rat brain.
Repeated treatment with fluoxetine and citalopram, which are potent 5-HT reuptake inhibitors, resulted in different regulation of 5-HT1A and 5-HT2 receptors in the rat brain. Their effects were compared with those of other antidepressants: imipramine, mianserin and levoprotiline. The density of 5-HT1A receptors, labelled with [3H]8-OH-DPAT, in the rat hippocampus was enhanced after citalopram, imipramine, mianserin and levoprotiline, but not altered after fluoxetine administration. [3H]Ketanserin binding sites, which label 5-HT2 receptors, were increased after fluoxetine and levoprotiline, but decreased after citalopram, imipramine and mianserin in the rat cerebral cortex. Acute administration of fluoxetine, but not citalopram, resulted in a decreased density of 5-HT1A receptors. 5-HT2 receptors were not changed by acute administration of either fluoxetine or citalopram. The obtained results indicate that besides 5-HT reuptake inhibiting properties of both compounds, there may exist an additional mechanism(s) of their action, which leads to different regulation of 5-HT1A and 5-HT2 receptors.
Klimek, V; Zak-Knapik, J; Mackowiak, M
Modulation by thyroid hormones of rat parotid amylase secretion stimulated by 5-hydroxytryptamine.
The effects of 5-hydroxytryptamine (5-HT) upon amylase secretion by rat parotid glands were studied in three groups of animals: (a) intact control rats (euthyroid rats); (b) hypothyroid rats obtained by surgical thyroidectomy 2 wk before the experiments; and (c) hyperthyroid rats obtained by the administration of sodium l-triiodothyronine for 2 wk before the experiments. Hyperthyroid rats showed significantly higher baseline amylase release than control rats. When the glands were stimulated with 5-HT (30 micro m), amylase release was significantly lower in the hypothyroid group and higher in the hyperthyroid rats than in control group. Addition of cholinergic, adrenergic or substance P antagonists did not modify 5-HT-stimulated amylase activity. The effects of 5-HT were partly but significantly blocked by the addition of 10 micro m methysergide (HT1/2/7 receptor blocker) in the three groups of rats. In contrast, 10 micro m ketanserine (HT2A receptor blocker) partly blocked the response to 5-HT only in the hyperthyroid animals. It was concluded that 5-HT induces amylase secretion by rat parotid glands through specific serotoninergic receptors, and that thyroid status modulates the 5-HT effect. PMID:14632685
Ostuni, Mariano AnĒbal; Houssay, Alberto Bernardo; Tumilasci, Omar Renķ
Increased levels of plasma 5-hydroxytryptamine in patients with coeliac disease.
In 17 patients with coeliac disease the 5-hydroxytryptamine (5-HT) concentration was measured in platelet-poor plasma (PPP) and in whole blood and compared with that of a control group of 30 healthy persons. The 5-HT level was determined by high-pressure liquid chromatography and electrochemical detection. In patients with coeliac disease the concentration of 5-HT in whole blood was elevated compared with the control group (p less than 0.001). The 5-HT level in PPP was significantly increased in patients with coeliac disease in whom the disease was untreated or treated with gluten-free diet for less than a year (p less than 0.01) but also compared with the patients with coeliac disease treated with a gluten-free diet for more than a year (p less than 0.01). In some untreated patients with newly diagnosed disease the 5-HT levels in PPP were markedly elevated and exceeded the levels ordinarily found in PPP in patients with carcinoid tumours. In these patients with coeliac disease the 5-HT concentration in PPP was reduced when the enteropathy was healed. There was no significant correlation between the 5-HT concentration in PPP versus whole blood in the different groups. PMID:4001841
Sj÷lund, K; Nobin, A
Chronic tryptophan deprivation attenuates gating deficits induced by 5-HT(1A), but not 5-HT? receptor activation.
The neurotransmitter serotonin (5-hydroxytryptamine; 5-HT) exerts a multifaceted function in the modulation of information processing, through the activation of multiple receptor families. In particular, stimulation of 5-HT(1A) and 5-HT(2A) receptors leads to sensorimotor gating impairments and perceptual perturbations. Previous evidence has shown that chronic deprivation of L-tryptophan (TRP), the precursor of 5-HT, results in marked reductions of 5-HT brain levels, as well as neuroplastic alterations in 5-HT(1A) and 5-HT(2A) expression and/or signaling. Building on these premises, in the present study we tested whether a prolonged TRP deprivation may differentially impact the roles of these receptors in the regulation of the prepulse inhibition (PPI) of the acoustic startle reflex, a dependable index of gating. Male Sprague-Dawley rats were fed for 14 days with either a regimen with negligible TRP content (TR-) or the same diet supplemented of TRP (TR+). At the end of this schedule, rats were treated with the prototypical 5-HT(1A) receptor agonist 8-OH-DPAT (62.5-250 ?g/kg, subcutaneous, s.c.) or the 5-HT? receptor agonist DOI (0.25-1 mg/kg, s.c.). Notably, the PPI deficits induced by 8-OH-DPAT in TR- rats were significantly milder than those observed in their TR+ counterparts; these effects were fully prevented by the 5-HT(1A) antagonist WAY-100135 (10 mg/kg, intraperitoneal). Conversely, TRP deprivation did not affect the PPI-disrupting properties of DOI. These findings suggest that prolonged 5-HT depletion attenuates the influence of 5-HT(1A), but not 5-HT? receptors on sensorimotor gating, confirming the distinct mechanisms of these two targets in PPI regulation. PMID:23141373
Stancampiano, Roberto; Frau, Roberto; Bini, Valentina; Collu, Maria; Carta, Manolo; Fadda, Fabio; Bortolato, Marco
The action of 5-hydroxytryptamine on chemoreceptor discharges of the cat's carotid body.
1 Chemoreceptor discharges were recorded in vivo from fine filaments of the carotid sinus nerve containing a single or several active units; their frequency was used as an index of receptor activity. The effects of 5-hydroxytryptamine (5-HT) on chemoreceptors were studied in 26 adult cats. At times, sinus baroreceptor discharges were recorded from the carotid nerve and the effect of 5-HT on the discharges was examined. 2 Intra-carotid injections of 5-HT (2-20 mug) induced a sharp and brief increase in chemoreceptor discharges, followed by depression or block which lasted for several seconds. Repeated injections at short intervals, and a small dose after a large dose of 5-HT resulted in depressed or blocked response to 5-HT. 3 5-HT in high doses (10-20 mug, i.a.) slightly depressed the chemoreceptor discharges induced by either acetylcholine (ACh) or NaCN, when these substances were applied within 20 s after 5-HT. 5-HT (5-20 mug, i.a.) applied during asphyxia induced a further increase in chemoreceptor discharges, soon followed by block of the discharges lasting for several seconds. 4 Atropine or hexamethonium in high doses did not change the chemoreceptor response to 5-HT, while that to ACh was markedly depressed. 5 (+)-Lysergic diethylamide (LSD), methysergide or gramine did not alter the response to 5-HT, while LSD in low doses produced a marked increase in chemoreceptor discharges. 6 Acute and chronic treatment with reserpine (5-10 mg/kg, i.v.) of the animals did not change the sensitivity and the reactivity of the chemoreceptor to ACh and NaCN, while the chemoreceptor response to 5-HT was augmented, indicating an increase in the sensitivity of chemoreceptors to 5-HT. 7 5-HT in small doses (2-10 mug, i.a.) induced a marked increase in sinus baroreceptor discharges; subsequently discharges were depressed or blocked for several seconds. 8 The results are discussed in relation to possible mechanism of action of 5-HT on the chemoreceptors. It is concluded that the exogenous 5-HT probably acts directly on the chemosensory nerve endings and depolarizes them, but 5-HT contained in the carotid body does not play a significant role in the generation of chemoreceptor discharges.
Nishi, K
The effect of DA-9701 on 5-hydroxytryptamine-induced contraction of feline esophageal smooth muscle cells.
Serotonin, or 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter found in blood platelets, the gastrointestinal (GI) tract, and the central nervous system (CNS) of animals and humans. The signaling pathways of 5-hydroxytryptamine (5-HT)-induced contractions in cat esophageal smooth muscle cell (ESMC)s have been identified, but the downstream components of the 5-HT signaling pathway remain unclear. DA-9701 is the standardized extract of the Pharbitis nil Choisy seed (Pharbitidis Semen, Convolvulaceae) and the root of Corydalis yahusuo W.T. Wang (Corydalis Tuber, Papaveraceae). DA-9701 is known to have strong gastroprokinetic effects and a good safety profile. In this study, we investigated the 5-HT signaling pathway at the G-protein level, and we explored the mechanisms by which DA-9701 induces smooth muscle contraction. Freshly isolated smooth muscle cells were harvested from the feline esophagus, and cells were permeabilized to measure their length. 5-HT produced esophageal smooth muscle contractions in a dose-dependent manner. Furthermore, 5-HT produced a relatively long-acting contraction. 5-HT binds to the 5-HT2, 5-HT3 and 5-HT4 receptors to induce smooth muscle contraction in feline ESMCs. These receptors, which are located in esophageal smooth muscle, are coupled to G?q, G?o and G?s. These G proteins activate PLC, which leads to Ca2+/calmodulin-dependent MLCK activation, resulting in MLC20 phosphorylation and cell contraction. Conversely, DA-9701 inhibits 5-HT-induced contraction by inhibiting MLC20 phosphorylation. PMID:24759073
Oh, Kyung Hoon; Nam, Yoonjin; Jeong, Ji Hoon; Kim, In Kyeom; Sohn, Uy Dong
5-hydroxytryptamine participation in the vagal inhibitory innervation of the stomach.
1. Intraluminal pressure was recorded from the isolated guinea-pig and mouse stomach with the vagus and sympathetic nerves attached.2. The response to vagal stimulation, which consists of an excitatory and an inhibitory component, resembled the response to 5-hydroxytryptamine (5-HT), which has no direct action on the muscle but acts on intrinsic excitatory and inhibitory ganglia.3. In the presence of hyoscine, the effect of vagal stimulation, of nicotinic compounds and of 5-HT were all purely relaxant. Competitive block of ganglionic receptors for acetylcholine reduced the vagal relaxation without antagonizing 5-HT. Specific desensitization of ganglionic receptors for 5-HT reduced the vagal relaxation without antagonizing nicotinic compounds.4. During the early phase of the blocking action of nicotine, responses to vagal stimulation and to 5-HT were both abolished. As the non-specific antagonism changed to the later phase of specific antagonism to acetylcholine, the inhibitory (but not the excitatory) component of the vagal response recovered partially, in parallel with the recovery of the relaxant effect of 5-HT.5. The vagal inhibitory effect was completely abolished only when competitive block of acetylcholine receptors was combined with desensitization of 5-HT receptors.6. Stimulation of the mouse stomach (after asphyxiation of the mucosa and exclusion of the luminal content) in the presence of hyoscine caused the release of 5-HT; this release was blocked by tetrodotoxin.7. The results, together with previous observations that 5-HT is contained within preganglionic nerve fibres in the myenteric plexus, are consistent with the hypothesis that 5-HT, with acetylcholine, may be a neurotransmitter in the vagal inhibitory innervation of the stomach. PMID:4383454
B³lbring, E; Gershon, M D
Unique allosteric regulation of 5-hydroxytryptamine receptor-mediated signal transduction by oleamide
The effects of oleamide, an amidated lipid isolated from the cerebrospinal fluid of sleep-deprived cats, on serotonin receptor-mediated responses were investigated in cultured mammalian cells. In rat P11 cells, which endogenously express the 5-hydroxytryptamine2A (5HT2A) receptor, oleamide significantly potentiated 5HT-induced phosphoinositide hydrolysis. In HeLa cells expressing the 5HT7 receptor subtype, oleamide caused a concentration-dependent increase in cAMP accumulation but with lower efficacy than that observed by 5HT. This effect was not observed in untransfected HeLa cells. Clozapine did not prevent the increase in cAMP elicited by oleamide, and ketanserin caused an ?65% decrease. In the presence of 5HT, oleamide had the opposite effect on cAMP, causing insurmountable antagonism of the concentration-effect curve to 5HT, but had no effect on cAMP levels elicited by isoproterenol or forskolin. These results indicate that oleamide can modulate 5HT-mediated signal transduction at different subtypes of mammalian 5HT receptors. Additionally, our data indicate that oleamide acts at an apparent allosteric site on the 5HT7 receptor and elicits functional responses via activation of this site. This represents a unique mechanism of activation for 5HT G protein-coupled receptors and suggests that G protein-coupled neurotransmitter receptors may act like their iontropic counterparts (i.e., ?-aminobutyric acid type A receptors) in that there may be several binding sites on the receptor that regulate functional activity with varying efficacies.
Thomas, Elizabeth A.; Carson, Monica J.; Neal, Michael J.; Sutcliffe, J. Gregor
Hypothalamic paraventricular 5-hydroxytryptamine inhibits the effects of ghrelin on eating and energy substrate utilization
Ghrelin microinjections into discrete regions of the hypothalamus, including the paraventricular nucleus (PVN), stimulate eating and promote carbohydrate oxidation, effects similar to PVN microinjection of neuropeptide Y (NPY). We have also reported that NPYÆs orexigenic and metabolic effects are antagonized by pretreatment with 5-hydroxytryptamine (5-HT) or 5-HT receptor agonists. In order to determine whether 5-HT also inhibits ghrelinÆs orexigenic and metabolic actions, the present study examined the effects of 5-HT pretreatment on ghrelin-induced alterations in eating and energy substrate utilization following direct injections into the hypothalamic PVN. Both 5-HT (5¢20 nmol) and ghrelin (100 pmol) were administered at the onset of the dark cycle. Food intake was measured 2 h postinjection. A separate group of rats (n=8) was injected with 5-HT paired with ghrelin and respiratory quotient (RQ; VCO2/VO2) was measured over 2 h using an open circuit calorimeter. PVN injections of ghrelin increased food intake and increased RQ, reflecting a shift in energy substrate utilization in favor of carbohydrate oxidation. 5-HT effectively blocked the effects of ghrelin on both food intake and RQ. We then administered the 5-HT2A/2C, receptor agonist, DOI, immediately prior to ghrelin. Similar to 5-HT, PVN DOI blocked ghrelin-induced eating and inhibited the peptideÆs effect on substrate utilization. These data are in agreement with other evidence suggesting that ghrelin functions as a gut-brain peptide in the control of food intake and energy metabolism, and indicate that 5-HT acts within the PVN to modulate ghrelinÆs orexigenic and metabolic signaling.
Currie, Paul J.; John, Catherine S.; Nicholson, Marjorie L.; Chapman, Colin D.; Loera, Katherine E.
Expression and function of 5HT 7 receptors in smooth muscle preparations from equine duodenum, ileum, and pelvic flexure
In horses, gastrointestinal (GI) disorders occur frequently and cause a considerable demand for efficient medication. 5-Hydroxytryptamine receptors (5-HT) have been reported to be involved in GI tract motility and thus, are potential targets for treating functional bowel disorders. Our studies extend current knowledge on the 5-HT7 receptor in equine duodenum, ileum and pelvic flexure by studying its expression throughout the
Andrea S. Prause; Michael H. Stoffel; Christopher J. Portier; Meike Mevissen
Menthol inhibits 5-HT3 receptor-mediated currents.
The effects of alcohol monoterpene menthol, a major active ingredient of the peppermint plant, were tested on the function of human 5-hydroxytryptamine type 3 (5-HT3) receptors expressed in Xenopus laevis oocytes. 5-HT (1 ?M)-evoked currents recorded by two-electrode voltage-clamp technique were reversibly inhibited by menthol in a concentration-dependent (IC50 = 163 ?M) manner. The effects of menthol developed gradually, reaching a steady-state level within 10-15 minutes and did not involve G-proteins, since GTP?S activity remained unaltered and the effect of menthol was not sensitive to pertussis toxin pretreatment. The actions of menthol were not stereoselective as (-), (+), and racemic menthol inhibited 5-HT3 receptor-mediated currents to the same extent. Menthol inhibition was not altered by intracellular 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid injections and transmembrane potential changes. The maximum inhibition observed for menthol was not reversed by increasing concentrations of 5-HT. Furthermore, specific binding of the 5-HT3 antagonist [(3)H]GR65630 was not altered in the presence of menthol (up to 1 mM), indicating that menthol acts as a noncompetitive antagonist of the 5-HT3 receptor. Finally, 5-HT3 receptor-mediated currents in acutely dissociated nodose ganglion neurons were also inhibited by menthol (100 ?M). These data demonstrate that menthol, at pharmacologically relevant concentrations, is an allosteric inhibitor of 5-HT3 receptors. PMID:23965380
Ashoor, Abrar; Nordman, Jacob C; Veltri, Daniel; Yang, Keun-Hang Susan; Shuba, Yaroslav; Al Kury, Lina; Sadek, Bassem; Howarth, Frank C; Shehu, Amarda; Kabbani, Nadine; Oz, Murat
5-HT1A/1B receptors as targets for optimizing pigmentary responses in C57BL/6 mouse skin to stress.
Stress has been reported to induce alterations of skin pigmentary response. Acute stress is associated with increased turnover of serotonin (5-hydroxytryptamine; 5-HT) whereas chronic stress causes a decrease. 5-HT receptors have been detected in pigment cells, indicating their role in skin pigmentation. To ascertain the precise role of 5-HT in stress-induced pigmentary responses, C57BL/6 mice were subjected to chronic restraint stress and chronic unpredictable mild stress (CRS and CUMS, two models of chronic stress) for 21 days, finally resulting in abnormal pigmentary responses. Subsequently, stressed mice were characterized by the absence of a black pigment in dorsal coat. The down-regulation of tyrosinase (TYR) and tyrosinase-related proteins (TRP1 and TRP2) expression in stressed skin was accompanied by reduced levels of 5-HT and decreased expression of 5-HT receptor (5-HTR) system. In both murine B16F10 melanoma cells and normal human melanocytes (NHMCs), 5-HT had a stimulatory effect on melanin production, dendricity and migration. When treated with 5-HT in cultured hair follicles (HFs), the increased expression of melanogenesis-related genes and the activation of 5-HT1A, 1B and 7 receptors also occurred. The serum obtained from stressed mice showed significantly decreased tyrosinase activity in NHMCs compared to that from nonstressed mice. The decrease in tyrosinase activity was further augmented in the presence of 5-HTR1A, 1B and 7 antagonists, WAY100635, SB216641 and SB269970. In vivo, stressed mice received 5-HT precursor 5-hydroxy-l-tryptophan (5-HTP), a member of the class of selective serotonin reuptake inhibitors (fluoxetine; FX) and 5-HTR1A/1B agonists (8-OH-DPAT/CP94253), finally contributing to the normalization of pigmentary responses. Taken together, these data strongly suggest that the serotoninergic system plays an important role in the regulation of stress-induced depigmentation, which can be mediated by 5-HT1A/1B receptors. 5-HT and 5-HTR1A/1B may constitute novel targets for therapy of skin hypopigmentation disorders, especially those worsened with stress. PMID:24586946
Wu, Hua-Li; Pang, Si-Lin; Liu, Qiong-Zhen; Wang, Qian; Cai, Min-Xuan; Shang, Jing
Evidence for distinct antagonist-revealed functional states of 5-hydroxytryptamine(2A) receptor homodimers.
The serotonin (5-hydroxytryptamine; 5-HT) 2A receptor is a cell surface class A G protein-coupled receptor that regulates a multitude of physiological functions of the body and is a target for antipsychotic drugs. Here we found by means of fluorescence resonance energy transfer and immunoprecipitation studies that the 5-HT(2A)-receptor homodimerized in live cells, which we linked with its antagonist-dependent fingerprint in both binding and receptor signaling. Some antagonists, like the atypical antipsychotics clozapine and risperidone, differentiate themselves from others, like the typical antipsychotic haloperidol, antagonizing these 5-HT(2A) receptor-mediated functions in a pathway-specific manner, explained here by a new model of multiple active interconvertible conformations at dimeric receptors. PMID:19279328
Brea, Josķ; Castro, Marißn; Giraldo, Jes·s; L¾pez-Gimķnez, Juan F; PadĒn, Juan Fernando; Quintißn, Fßtima; Cadavid, Maria Isabel; Vilar¾, Maria Teresa; Mengod, Guadalupe; Berg, Kelly A; Clarke, William P; Vilardaga, Jean-Pierre; Milligan, Graeme; Loza, Maria Isabel
Serotonin (5-HT) activation of immortalized hypothalamic neuronal cells through the 5-HT1B serotonin receptor.
Serotonin [or 5-hydroxytryptamine or (5-HT)] has been implicated as a key modulator in energy homeostasis and a primary focus in the treatment of obesity. There is growing evidence that 5-HT, acting through the 5-HT 1B receptor (5-HT(1B)R) in the paraventricular nucleus of the hypothalamus (PVN), is important to this regulation. However, there is some contention as to whether 5-HT(1B)R action occurs directly on PVN neurons or indirectly via inhibitory inputs into the PVN. To address these questions, we used a novel clonal, hypothalamic neuronal cell model, adult mouse hypothalamic-2/30 (mHypoA-2/30), expressing a PVN-specific marker, single-minded homolog 1, as well as a complement of PVN neuropeptides, including TRH, vasopressin, ghrelin, nucleobindin-2, and galanin. Adult mouse hypothalamic-2/30 neurons were also found to express the 5-HT(1B)R and 5-HT 6 receptor, but not 2C, all previously linked to feeding regulation. Direct serotonergic stimulation (100 nm to 10 ?m) of these neurons resulted in dose-dependent cFos activation. 5-HT (10 ?m) suppressed forskolin-induced cAMP levels and induced a rise in intracellular Ca(2+) through ER Ca(2+) release, effects that were mimicked by the 5-HT(1B)R agonists, CGS12066B and CP93129, and that were attenuated in the presence of the 5-HT(1B)R-specific inhibitors, GR55562 and isamoltane hemifumarate. Modest transcriptional changes in ghrelin and nucleobindin-2 were also observed in response to 100 nm and 10 ?m 5-HT, respectively. These findings support the model wherein 5-HT action through the 1B receptor subtype occurs directly on PVN neurons, leading to potential modification of neuronal transcriptional and secretory machinery. PMID:22919062
Tung, Stephanie; Hardy, Alexandre B; Wheeler, Michael B; Belsham, Denise D
Molecular and Pharmacological Characterization of Serotonin 5-HT2? and 5-HT7 Receptors in the Salivary Glands of the Blowfly Calliphora vicina
Secretion in blowfly (Calliphora vicina) salivary glands is stimulated by the biogenic amine serotonin (5-hydroxytryptamine, 5-HT), which activates both inositol 1,4,5-trisphosphate (InsP3)/Ca2+ and cyclic adenosine 3?,5?-monophosphate (cAMP) signalling pathways in the secretory cells. In order to characterize the signal-inducing 5-HT receptors, we cloned two cDNAs (Cv5-ht2?, Cv5-ht7) that share high similarity with mammalian 5-HT2 and 5-HT7 receptor genes, respectively. RT-PCR demonstrated that both receptors are expressed in the salivary glands and brain. Stimulation of Cv5-ht2?-transfected mammalian cells with 5-HT elevates cytosolic [Ca2+] in a dose-dependent manner (EC50?=?24 nM). In Cv5-ht7-transfected cells, 5-HT produces a dose-dependent increase in [cAMP]i (EC50?=?4 nM). We studied the pharmacological profile for both receptors. Substances that appear to act as specific ligands of either Cv5-HT2? or Cv5-HT7 in the heterologous expression system were also tested in intact blowfly salivary gland preparations. We observed that 5-methoxytryptamine (100 nM) activates only the Cv5-HT2? receptor, 5-carboxamidotryptamine (300 nM) activates only the Cv5-HT7 receptor, and clozapine (1 ĄM) antagonizes the effects of 5-HT via Cv5-HT7 in blowfly salivary glands, providing means for the selective activation of each of the two 5-HT receptor subtypes. This study represents the first comprehensive molecular and pharmacological characterization of two 5-HT receptors in the blowfly and permits the analysis of the physiological role of these receptors, even when co-expressed in cells, and of the modes of interaction between the Ca2+- and cAMP-signalling cascades.
Roser, Claudia; Jordan, Nadine; Balfanz, Sabine; Baumann, Arnd; Walz, Bernd; Baumann, Otto; Blenau, Wolfgang
Inhibition of the Serotonin (5Hydroxytryptamine) Transporter Reduces Bone Accrual during Growth
Selective serotonin-reuptake inhibitors (SSRIs) antagonize the serotonin (5-hydroxytryptamine) transporter (5-HTT), and are frequently prescribed to children and adolescents to treat depression. However, recent findings of functional se- rotonergic pathways in bone cells and preliminary clinical evidence demonstrating detrimental effects of SSRIs on bone growth have raised questions regarding the effects of these drugsonthegrowingskeleton.Thecurrentworkinvestigated the impact of 5-HTT inhibition on the
Stuart J. Warden; Alexander G. Robling; Megan S. Sanders; Michael M. Bliziotes; Charles H. Turner
Photoreactivity of LY277359 maleate, a 5-hydroxytryptamine3 (5-HT3) receptor antagonist, in solution.
Compound LY277359 maleate undergoes a photoinduced solvolysis reaction in water to generate the corresponding hydroxylated product and release chloride. Attempts to stabilize a parenteral formulation of the compound led to an investigation of possible reaction mechanisms. The data are consistent with a mechanism involving homolytic cleavage of the aryl-chloride bond followed by electron transfer to give an aryl cation intermediate. The cation thus formed reacts with surrounding nucleophiles to give the substituted product. A kinetic expression for reaction rate was derived from the mechanism, and various components of the rate constant were evaluated experimentally. The reaction is slowed with the addition of chloride, presumably via a common ion effect (enhanced retroreaction). In the absence of added chloride, the reaction can be described kinetically by an initiation term. An inner filter effect is also observed, where increasing amounts of the hydroxylated product slow the reaction. Experimental data for observed rate constants as a function of starting concentration and light intensity are fit with good correlation to an equation describing the filter effect. Additional studies evaluated the effects of various structural features of the parent compound on the rate of the reaction in glass containers. It was determined that reactivity was dependent on two features: (1) the ortho positioning of the carboxyl and ether groups, which shifted an absorption band above the container cutoff; and (2) the para orientation of the chloro group to the ether, which is para activating in the photoexcited state. PMID:1796037
Mosher, G L; McBee, J
Venlafaxine: acute and chronic effects on 5-hydroxytryptamine levels in rat brain in vivo.
Venlafaxine is a dual serotonin (5-hydroxytryptamine, 5-HT) and noradrenaline uptake inhibitor which has been claimed to have an onset of antidepressant action which is faster than for other comparable drugs. The effects of venlafaxine on brain 5-HT levels in vivo have not yet been examined. Acute administration of venlafaxine to rats by i.p. injection resulted in dose-dependent increases in cortical and hippocampal 5-HT levels, as measured by in vivo microdialysis, over the range 5-20 mg/kg. The effect of venlafaxine (10 mg/kg i.p.) was potentiated by prior administration of pindolol (10 mg/kg s.c.) in hippocampus but not in frontal cortex. Daily administration of venlafaxine (5 mg/kg i.p.) for 4 weeks did not change basal 5-HT levels in either brain area. The effect of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 0.2 mg/kg s.c.) to reduce 5-HT levels was unaffected by chronic venlafaxine at this dose, indicating that there was no change in sensitivity of presynaptic 5-HT1A autoreceptors. PMID:10374710
Gur, E; Dremencov, E; Lerer, B; Newman, M E
A morphological study of the effects of 5-hydroxytryptamine and indomethacin on rat mesenteric venules.
A method is described for preparing venules of the rat mesentery for electron microscopy after the application of 5-hydroxytryptamine (5-HT) and pretreatment with indomethacin. Local application of 5-HT caused the leakage of colloidal carbon and the emigration of leucocytes into the venule wall. 5-HT also caused endothelial cells to bulge and their nuclei to contort. It increased the number of protrusions on both the luminal and abluminal surfaces of the endothelium and increased the width of the subendothelial space, and the degree of vesiculation in the endothelial cells. Systemic treatment with indomethacin significantly decreased the amount of carbon passing through the endothelium after the local application of 5-HT, but enhanced some of the other effects of 5-HT. Thus it increased the bulging of endothelial cells and contortion of their nuclei, and further increased the number of surface protrusions and the subendothelial space. It had no effect on the emigration of leucocytes resulting from the application of 5-HT. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5
Northover, A. M.
Reconstitution of the human placental 5-hydroxytryptamine transporter in a catalytically active form after detergent solubilization.
The 5-hydroxytryptamine (5-HT; serotonin) transporter was solubilized from purified human placental brush border membranes by cholate in the presence of urea, and the solubilized transporter was reconstituted into proteoliposomes in a functionally active form. Solubilization of the membranes with cholate in the absence of urea inactivated the transporter. The reconstitution procedure involved precipitation of the solubilized proteins and simultaneous removal of cholate and urea by poly(ethylene glycol), and incorporation of the precipitated proteins into proteoliposomes in the presence of asolectin by a freeze-thaw/sonication technique. Optimal conditions included the use of 6% poly(ethylene glycol) during the precipitation step and an asolectin/protein ratio of 10:1 during the reconstitution step. K+ was present in the reconstitution medium. The reconstituted proteoliposomes showed the ability to transport 5-HT against a concentration gradient when an inwardly directed NaCl gradient was imposed. The 5-HT transport system in the proteoliposomes had an absolute requirement for Na+ and Cl-. The system was specific for 5-HT and was inhibited by imipramine, paroxetine and fluoxetine. The Na+/Cl-/5-HT stoichiometry was found to be 1:1:1. The transport process was electrically silent, indicating that one K+ ion was countertransported for each 5-HT molecule. The reconstituted 5-HT transporter showed high affinity for 5-HT, with an apparent Michaelis-Menten constant of 0.34 +/- 0.01 microM. It is concluded that the human placental 5-HT transporter can be solubilized and reconstituted into proteoliposomes in a transport-competent form and that the characteristics of the reconstituted transporter are similar to those of the native transporter.
Ramamoorthy, S; Cool, D R; Leibach, F H; Mahesh, V B; Ganapathy, V
The inhibitory effects of 5-hydroxytryptamine on gastric acid secretion by the rat isolated stomach.
1 The effect of 5-hydroxytryptamine (5-HT) on acid secretion by a rat isolated stomach preparation has been studied. 2 5-HT at 10(-5)M in the serosal bathing fluid produced significant inhibition of the acid secretory responses to histamine, pentagastrin and isoprenaline but was without effect on basal secretion or that due to bethanechol, dibutryl cyclic adenosine 3',5'-monophosphate (db cyclic AMP) or phosphodiesterase inhibition with ICI63197. Increasing the concentration of 5-HT to 5 x 10(-5) M did not change this pattern of response whilst 5-HT at 10(-6) M did not cause consistent inhibition. 3 The inhibitory action of 5-HT could be prevented by the antagonist methysergide (2.5 x 10(-5) M). This concentration of methysergide alone did not affect responses to secretagogues or basal acid output. 4 Neither propranolol (2.5 x 10(-5) M) nor tetrodotoxin (10(-6) M) antagonized the inhibitory action of 5-HT. 5 Both indomethacin (2.8 x 10(-5) M) and ibuprofen (2.4 x 10(-4) M) antagonized the action of 5-HT. Indomethacin alone had no effect upon secretagogue responses. 6 5-HT at 10(-5) M had no inhibitory action when applied to the mucosal side of the preparation. 7 The results indicate that 5-HT can act directly on the stomach of the rat to produce inhibition of acid output. This inhibition is selective and may involve the products of cyclo-oxygenase activity. PMID:6824810
Canfield, S P; Spencer, J E
The 5-HT3 receptor is a member of the Cys-loop family of ligand-gated ion channels. These receptors are located in both the peripheral and central nervous systems, where functional receptors are constructed from five subunits. These subunits may be the same (homopentameric 5-HT3A receptors) or different (heteropentameric receptors, usually comprising of 5-HT3A and 5-HT3B receptor subunits), with the latter having a number of distinct properties. The 5-HT3 receptor binding site is comprised of six loops from two adjacent subunits, and critical ligand binding amino acids in these loops have been largely identified. There are a range of selective agonists and antagonists for these receptors and the pharmacophore is reasonably well understood. There are also a wide range of compounds that can modulate receptor activity. Studies have suggested many diverse potential disease targets that might be amenable to alleviation by 5-HT3 receptor selective compounds but to date only two applications have been fully realised in the clinic: the treatment of emesis and irritable-bowel syndrome.
Thompson, A. J.; Lummis, S. C. R.
5-hydroxytryptamine stimulates glucose transport in cardiomyocytes via a monoamine oxidase-dependent reaction.
This study deals with the effect of 5-hydroxytryptamine (5-HT; serotonin) on glucose transport in isolated rat cardiac myocytes. In these cells, 5-HT (10-300 microns), as well as tryptamine, 5-methoxytryptamine and dopamine, elicited a 3-5 fold increase in glucose transport, as compared with control. This effect was maximal after 90 min, and was concomitant with a 1.8- and 1.5-fold increase in the amounts of glucose transporters GLUT1 and GLUT4 at the cell surface of the cardiomyocytes, as determined by using the photoaffinity label 3H-2-N-[4-(1-azi-2,2,2-trifluoroethyl)benzoyl]-1,3-bis-(D-manno s-4-yl) propyl-2-amine (3H-ATB-BMPA). In contrast, 3-3000 microM of the selective 5-HT receptor agonists 5-carboxyamido-tryptamine, alpha-methyl-serotonin, 2-methyl-serotonin or renzapride failed to stimulate glucose transport. The effect of 5-HT was not affected by (i) the 5-HT receptor antagonists methysergide (1 microM), ketanserin (1 microM), cyproheptadine (1 microM), MDL 72222 (1 microM) or ICS 205-930 (3 microM), nor by (ii) the adrenergic receptor antagonists prazosin (1 microM), yohimbine (1 microM) or propranolol (5 microM), nor by (iii) the dopaminergic antagonists SCH 23390 (1 microM) or haloperidol (1 microM). The monoamine oxidase inhibitors clorgyline (1 microM) and tranylcypromine (1 microM) completely suppressed the effect of 5-HT, whereas the control and insulin-stimulated rates of glucose transport were unaffected. Addition of catalase or glutathione diminished the 5-HT-dependent stimulation of glucose transport by 50%; these two factors are known to favour the degradation of H2O2 (which can be formed during the deamination of amines by monoamine oxidases). Glutathione also depressed the stimulatory action of exogenously added H2O2 (20 microM) by 30%. Furthermore, in cells treated with 5_HT, a time-dependent accumulation of 5-hydroxy-1H-indol-3-ylacetic acid (a product of 5-HT metabolism via monoamine oxidases) was observed, which paralleled the changes in glucose transport. In conclusion, the stimulation of glucose transport by 5-HT in cardiomyocytes is not mediated by a 5-HT1, 5-HT2, 5-HT3 or 5-HT4 receptor, nor by an adrenergic or dopaminergic receptor, but is likely to occur through the degradation of by a monoamine oxidase and concomitant formation of H2O2.
Fischer, Y; Thomas, J; Kamp, J; Jungling, E; Rose, H; Carpene; Kammermeier, H
Biochemical and pharmacological properties of SR 46349B, a new potent and selective 5-hydroxytryptamine2 receptor antagonist.
A new potent, selective and p.o. active serotonergic [5-hydroxytryptamine (5-HT2)] receptor antagonist, SR 46349B [trans, 4-([3Z)3-(2-dimethylaminoethyl)oxyimino-3(2-flurophenyl++ +)propen-1-yl]phenol hemifumarate) has been characterized by a series of "in vitro" and "in vivo" methods. Based upon binding studies with 5-HT2 receptors in rat brain cortical membranes and blockade of 5-HT-induced contractions in isolated tissues (rabbit thoracic aorta, rat jugular vein, rat caudal artery, rat uterus and guinea pig trachea), SR 46349B showed high affinity for 5-HT2 receptors. Furthermore, SR 46349B displayed moderate affinity for the 5-HT1C receptor and had no affinity for the other 5-HT1 subclass (5-HT1A, 5-HT1B or 5-HT1D), dopamine (D1 or D2), "alpha" adrenergic (alpha-1 or alpha-2), sodium and calcium channel and histamine (H1) receptors. It did not interact with histamine (H1), alpha-1 adrenergic and 5-HT3 receptors in smooth muscle preparations. No inhibition of the uptake of norepinephrine, dopamine or 5-HT was seen. Based upon blockade of pressor responses to 5-HT in pithed rats and in vivo binding studies in mice, SR 46349B was found to be a potent and p.o. active 5-HT2 receptor antagonist with a relatively long duration of action. Behavioral experiments, including mescaline- and 5-hydroxytryptophan-induced head twitches and learned helplessness, as well as sleep-waking cycle and EEG spectral parameter studies, indicated that SR 46349B has a classical 5-HT2 psychopharmacological antagonist profile. PMID:1501121
Rinaldi-Carmona, M; Congy, C; Santucci, V; Simiand, J; Gautret, B; Neliat, G; Labeeuw, B; Le Fur, G; Soubrie, P; Breliere, J C
The role of the 5HT 2A and 5HT 2C receptors in the stimulus effects of hallucinogenic drugs III: the mechanistic basis for supersensitivity to the LSD stimulus following serotonin depletion
The present study was designed to determine the effects ofp-chlorophenylalanine (PCPA) andp-chloroamphetamine (PCA) administration on (1) the levels of serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in rat brain, (2) the sensitivity of LSD-trained rats to the stimulus effects of LSD, and (3) the maximal levels of 5-HT2A and 5-HT2C receptor mediated phosphoinositide (PI) hydrolysis in rat brain. PCA and
D. Fiorella; S. Helsley; D. S. Lorrain; R. A. Rabin; J. C. Winter
In vivo criteria to differentiate monoamine reuptake inhibitors from releasing agents: sibutramine is a reuptake inhibitor.
Because monoamine reuptake inhibitors and releasing agents both increase extracellular neurotransmitter levels, establishing in vivo experimental criteria for their classification has been difficult. Using microdialysis in the hypothalamus of unanesthetized rats, we provide evidence that serotonin- (5-HT) selective and nonselective reuptake inhibitors can be distinguished from the 5-HT-releasing agent fenfluramine by four criteria: 1) Systemic fenfluramine produces a much greater increase in 5-HT than the reuptake inhibitors. 2) The 5-HT somatodendritic autoreceptor agonist, (+/-)-8-hydroxy-(dipropylamino)tetralin (8-OH-DPAT), attenuates the increase in 5-HT produced by reuptake inhibitors, but not by fenfluramine. 3) The large increase in 5-HT produced by infusion of reuptake inhibitors into the hypothalamus is attenuated by their systemic administration. However, systemic injection of fenfluramine during its local infusion does not attenuate this increase. 4) Reuptake inhibitor pretreatment attenuates fenfluramine-induced increases in 5-HT. According to these criteria, the in vivo effects of the novel antiobesity drug sibutramine are consistent with its characterization as a 5-HT reuptake inhibitor and not a 5-HT releaser. Thus, sibutramine produced increases in hypothalamic 5-HT similar in magnitude to the effects of the known reuptake inhibitors, and the increase was attenuated by 8-OH-DPAT. Also, sibutramine attenuated fenfluramine-induced 5-HT release. Systemic administration of sibutramine failed to attenuate the increase in 5-HT produced by its local infusion, suggesting that this criterion is not applicable to compounds with low affinity for the 5-HT transporter. PMID:9353373
Gundlah, C; Martin, K F; Heal, D J; Auerbach, S B
Comparative Study of Pre and Postsynaptic 5HT1A Receptor Modulation of Anxiety in Two Ethological Animal Tests
The purpose of this study was to determine the roles of the presynaptic 5-hydroxytryptamine1A (5-HT1A) receptors in the median raphenucleus (MRN) and of the postsynaptic 5-HT1A receptors in its projection area of the dorsal hippocampus in the social interaction and elevated plus-maze tests of anxiety. Direct administration of the 5-HT1A receptor agonist (6)-8- hydroxy-dipropylaminotetralin (8-OH-DPAT, 200 ng) into the MRN
Sandra E. File; Luis E. Gonzalez; Nick Andrews
Central 5HT7 receptors are critical for reflex activation of cardiac vagal drive in anaesthetized rats
5-Hydroxytryptamine (5-HT; serotonin)-containing neurones contribute to reflex activation of parasympathetic outflow in a number of species, but the 5-HT receptors mediating these effects have yet to be fully determined. The present experiments demonstrate that central 5-HT7 receptors are involved in the vagal bradycardia evoked during the cardiopulmonary reflex, baroreflexes and the chemoreflex, as well as other autonomic changes caused by
Daniel O. Kellett; G. Ramage; David Jordan
Correlation between 5HT7 receptor affinity and protection against sound-induced seizures in DBA\\/2J mice
Audiogenic seizures can be induced in DBA\\/2J mice following intense auditory stimulation. A number of neurotransmitters, including\\u000a 5-hydroxytryptamine (5-HT), are believed to be involved in mediating this effect since it has been shown previously that depletion\\u000a of 5-HT or blockade of 5-HT receptors protects DBA\\/2J mice from these audiogenic seizures. The present study was undertaken\\u000a to determine whether antagonism of
Anne Bourson; Vķronique Kapps; Catherine Zwingelstein; Alain Rudler; Frank G. Boess; A. J. Sleight
Changes in systemic and regional haemodynamics during 5HT7 receptor-mediated depressor responses in rats
The 5-hydroxytryptamine (5-HT)-induced late depressor response in rats is mainly mediated by vascular 5-HT7 receptors. The present study was devoted to determining the systemic and regional haemodynamic changes during this response,\\u000a with particular emphasis on localising vascular beds that may contribute to the increase in total systemic vascular conductance.\\u000a In vagosympathectomised, pentobarbital-anaesthetised rats pretreated with the 5-HT2 receptor antagonist ritanserin
Peter De Vries; Pieter A. De Visser; Jan P. C. Heiligers; Carlos M. Villal¾n; P. R. Saxena
Effect of prolonged administration of tianeptine on 5HT neurotransmission: an electrophysiological study in the rat hippocampus and dorsal raphe
Extracellular unitary recordings of dorsal hippocampus CA3 pyramidal neurons and of dorsal raphe 5-hydroxytryptamine (5-HT) neurons were used to assess the effect of tianeptine, a putative antidepressant, on the efficacy of 5-HT neurotransmission. Sustained tianeptine administration (20 mg\\/kg\\/day, s.c. ū 14 days) did not modify the firing activity of 5-HT neurons in the dorsal raphe. Their responsiveness to the intravenous
Graciela Pi±eyro; Lyne Deveault; Claude Montigny; Pierre Blier
Desensitization and down-regulation of the 5-hydroxytryptamine1B receptor in the opossum kidney cell line.
In the opossum kidney cell line the 5-hydroxytryptamine (serotonin; 5-HT)1B receptor is negatively coupled to adenylyl cyclase via a Gi protein. Preincubation of opossum kidney cell line cell monolayers with 5-HT resulted in 5-HT1B receptor-mediated desensitization expressed as a 4-fold rightward shift of the dose-response curve and a 10 to 29% decrease of maximal inhibition of forskolin-stimulated cyclic AMP production. These moderate decreases in potency and efficacy were concentration- and time-dependent. Maximal desensitization occurred with 3 hr of 5-HT preincubation. Preincubation with 5-HT caused no change in the potency or efficacy of alpha-2 adrenergic agonist-mediated inhibition of forskolin-stimulated cyclic AMP production. Therefore, the desensitization caused by 5-HT preincubation appears to be homologous. Down-regulation of the 5-HT1B receptor, assessed with the high affinity radioligand [125I]iodocyanopindolol, also occurred, and was concentration- and time-dependent. Maximum down-regulation of 40% occurred after 20 hr of exposure to 10 microM 5-HT. These results demonstrate that, like other receptors coupled to the inhibition of adenylyl cyclase, exposure of 5-HT1B receptors to an agonist causes desensitization of the functional response followed by down-regulation of the receptor. PMID:1313870
Pleus, R C; Bylund, D B
A 5HT7 Receptor-Mediated Depolarization in the Anterodorsal Thalamus. I. Pharmacological Characterization
Little is currently known regarding the electrophysiological re- sponse elicited by 5-hydroxytryptamine-7 (5-HT7) receptor stimulation in the brain. Previous anatomical studies have shown that the anterior thalamus expresses a high density of 5-HT7 receptors. Therefore, we used whole-cell recording tech- niques in the in vitro brain slices to examine the effects of serotonin on neurons of the anterodorsal nucleus of
Pharmacological characterisation of 5HT receptors positively coupled to adenylyl cyclase in the rat hippocampus
The pharmacological properties of 5-hydroxytryptamine (5-HT) receptors positively coupled to adenylyl cyclase in the rat hippocampus\\u000a were investigated using selective agonists and antagonists. 5-HT (0.008¢125 ?M) stimulated cyclic AMP formation in homogenates\\u000a of rat hippocampus in a concentration-dependent manner. The maximal increase in cyclic AMP formation occurred at 1 ?M (141\\u000a ? 6%) and the half-maximal effect (EC50) at 50
Rudolf Markstein; Machiko Matsumoto; Christian Kohler; Hiroko Togashi; Mitsuhiro Yoshioka; Daniel Hoyer
Cholesterol depletion reduces serotonin binding and signaling via human 5HT 7(a) receptors
Lipids, including cholesterol, are critical components of the cell membrane where they are enriched in microdomains, lipid rafts, which organize and concentrate receptors and intracellular proteins involved in signal transduction. The present study examined the effects of cholesterol depletion on serotonin (5-HT) binding and signaling via 5-hydroxytryptamine7 (5-HT7) receptors in stably transfected HeLa cells. Immunohistochemical, ligand-binding and biotinylation experiments demonstrated
Benita Sj÷gren; Mark W. Hamblin; Per Svenningsson
Multiple 5-HT receptors in the guinea-pig superior cervical ganglion.
1. We have studied the pharmacology of the depolarization by 5-hydroxytryptamine (5-HT) of the guinea-pig isolated superior cervical ganglion (SCG) using the grease-gap technique. We studied the effects of selective and non-selective antagonists on the responses to 5-HT and other 5-HT receptor agonists. 2. We have extended the pharmacology of the 5-HT3 receptor in this preparation by studying the effects of granisetron, BRL 46470 and mianserin on the concentration-response curve (CRC) to 2-methyl-5-HT. As with other 5-HT3 receptor antagonists, these compounds exhibited a lower affinity for guinea-pig 5-HT3 receptors than for rat 5-HT3 receptors. 3. We have confirmed that low concentrations of 5-HT (< or = 1 microM) mediate ketanserin-sensitive responses and higher concentrations of 5-HT also recruit 5-HT3 receptors. The responses to low concentrations of 5-HT were antagonized by low concentrations of ketanserin, spiperone, mianserin, DOI and LSD indicating probably mediation by 5-HT2A receptors. At high concentrations, the hallucinogen, DOI, but not LSD, evoked a ketanserin-sensitive depolarization. 4. Although mianserin could bind to the 5-HT2A receptors in this preparation, we could not demonstrate a down-regulation of depolarizations evoked by these receptors after a 10 day oral treatment with mianserin (10 mg kg-1, daily). 5. 5-Carboxamidotryptamine (5-CT) evoked a prolonged depolarization. Although high concentrations of 5-CT (> or = microM) appeared to activate 5-HT2A receptors, lower concentrations of 5-CT evoked a response with a distinct pharmacology. After studying the action of 20 selective and non-selective 5-HT receptor ligands we believe that this response may be mediated by a novel receptor; but its pharmacology is closest to that of receptors in the 5-HT2 receptor family. Like 5-CT, 5-HT (3-300 microM) could evoke an LSD-sensitive response in the presence of the 5-HT2 receptor antagonist, ketanserin and the 5-HT3 receptor antagonist, tropisetron (all 1 microM). 6. We conclude that 5-HT activates three pharmacologically distinct receptors to depolarize the guinea-pig SCG. Low concentrations of 5-HT appear to activate 5-HT2A receptors. Higher concentrations of 5-HT also activate 5-HT3 receptors and a possible novel 5-HT receptor. The novel receptor could be a species homologue of a 5-HT2 receptor or an, as yet, unclassified 5-HT receptor.
Watkins, C. J.; Newberry, N. R.
5-Hydroxytryptamine 4(a) receptor expressed in Sf9 cells is palmitoylated in an agonist-dependent manner.
The mouse 5-hydroxytryptamine 4(a) receptor [5-HT(4(a))] was expressed with a baculovirus system in insect cells and analysed for acylation. [(3)H]Palmitic acid was effectively incorporated into 5-HT(4(a)) and label was sensitive to the treatment with reducing agents indicating a thioester-type bond. Analysis of protein-bound fatty acids revealed that 5-HT(4(a)) contains predominantly palmitic acid. Treatment of infected Sf9 (Spodoptera frugiperda) cells with BIMU8 [(endo-N-8-methyl-8-azabicyclo[3.2.1]oct-3-yl)-2,3-dehydro-2-oxo-3-(prop-2-yl)-1H-benzimid-azole-1-carboxamide], a 5-HT(4) receptor-selective agonist, generated a dose-dependent increase in [(3)H]palmitate incorporation into 5-HT(4(a)) with an EC(50) of approx. 10 nM. The change in receptor labelling after stimulation with agonist was receptor-specific and did not result from general metabolic effects. We also used both pulse labelling and pulse-chase labelling to address the dynamics of 5-HT(4(a)) palmitoylation. Incorporation studies revealed that the rate of palmitate incorporation was increased approx. 3-fold after stimulation with agonist. Results of pulse-chase experiments show that activation with BIMU8 promoted the release of radiolabel from 5-HT(4(a)), thereby reducing the levels of receptor-bound palmitate to approximately one-half. Taken together, our results demonstrate that palmitoylation of 5-HT(4(a)) is a reversible process and that stimulation of 5-HT(4(a)) with agonist increases the turnover rate for receptor-bound palmitate. This provides evidence for a regulated cycling of receptor-bound palmitate and suggests a functional role for palmitoylation/depalmitoylation in 5-hydroxytryptamine-mediated signalling.
Ponimaskin, E G; Schmidt, M F; Heine, M; Bickmeyer, U; Richter, D W
The facilitatory actions of 5-hydroxytryptamine and bradykinin in the superior cervical ganglion of the rabbit
1 The effects of 5-hydroxytryptamine (5-HT) on ganglionic transmission and on intrinsic modulation of transmission have been re-examined and compared with the effects of bradykinin by means of electrophysiological techniques. 2 Early facilitation, which is maximal 40-75 ms after a conditioning stimulus, was considerably enhanced by 5-HT. This enhancement was concentration-dependent, the threshold concentration lying between 0.1 and 1 ?M. With concentrations of 5-HT 10 ?M or greater, there was some depression of the Sa response to the conditioning stimulus. 3 5-HT reduced or abolished the inhibition of a test response induced by a conditioning response 100-300 ms earlier. Facilitation was observed at these intervals at concentrations of 5-HT of 25 ?M or greater. 4 Late facilitation, which is maximal 700-2000 ms after a conditioning stimulus, was increased by 5-HT, but the effect was not as great as on early facilitation and was not always seen with a concentration of 1 ?M. 5 Bradykinin reduced early facilitation but increased the amplitude of the transmitted action potential in response to a single stimulus. The threshold concentration producing these effects was between 1 and 2 ?M. 6 5-HT produced a rapid depolarization of the ganglion cell membrane which was followed by an after-hyperpolarization. 7 Bradykinin either produced no measurable change in ganglion cell resting potential or only very small, transient depolarizations. 8 The depression of transmission, enhancement of intrinsic facilitation and the depolarization of the ganglion cell membrane induced by 5-HT may indicate more than one mode of action of this amine at the ganglionic synapse.
Wallis, D.I.; Woodward, B.
The 5-hydroxytryptamine 4 Receptor Agonist-induced Actions and Enteric Neurogenesis in the Gut.
We explored a novel effect of 5-hydroxytryptamine 4 receptor (5-HT4R) agonists in vivo to reconstruct the enteric neural circuitry that mediates a fundamental distal gut reflex. The neural circuit insult was performed in guinea pigs and rats by rectal transection and anastomosis. A 5-HT4R-agonist, mosapride citrate (MOS) applied orally and locally at the anastomotic site for 2 weeks promoted the regeneration of the impaired neural circuit or the recovery of the distal gut reflex. MOS generated neurofilament-, 5-HT4R- and 5-bromo-2'-deoxyuridine-positive cells and formed neural network in the granulation tissue at the anastomosis. Possible neural stem cell markers increased during the same time period. These novel actions by MOS were inhibited by specific 5-HT4R-antagonist such as GR113808 (GR) or SB-207266. The activation of enteric neural 5-HT4R promotes reconstruction of an enteric neural circuit that involves possibly neural stem cells. We also succeeded in forming dense enteric neural networks by MOS in a gut differentiated from mouse embryonic stem cells. GR abolished the formation of enteric neural networks. MOS up-regulated the expression of mRNA of 5-HT4R, and GR abolished this upregulation, suggesting MOS differentiated enteric neural networks, mediated via activation of 5-HT4R. In the small intestine in H-line: Thy1 promoter green fluorescent protein (GFP) mice, we obtained clear 3-dimensional imaging of enteric neurons that were newly generated by oral application of MOS after gut transection and anastomosis. All findings indicate that treatment with 5-HT4R-agonists could be a novel therapy for generating new enteric neurons to rescue aganglionic disorders in the whole gut. PMID:24466442
Takaki, Miyako; Goto, Kei; Kawahara, Isao
Differential activation of the 5-hydroxytryptamine-containing neurons of the midbrain raphe of the rat in response to randomly presented inescapable sound
Estimates of 5-hydroxytryptamine (5-HT) turnover in response to 30 min of inescapable, randomly presented, loud sound (sound stress) were obtained for regions of rat brain containing 5-HT perikarya by means of 5-hydroxytryptophan (5-HTP) accumulation after administration of an inhibitor of aromatic amino acid decarboxylase (100 mg\\/kg i.p., m-hydroxybenzylhydrazine, NSD 1015). Sound stress increased 5-HTP accumulation in the median raphe nucleus
Roger P. Dilts; Margaret C. Boadle-Biber
Effects of nitric oxide in 5-hydroxytryptamine-, cholera toxin-, enterotoxigenic Escherichia coli- and Salmonella Typhimurium-induced secretion in the porcine small intestine
The effects of nitric oxide (NO) in the secretory response to the endogenous secretagogue 5-hydroxytryptamine (5-HT), the enterotoxins heat-labile enterotoxigenic Escherichia coli (ETEC) toxin (LT) and cholera toxin (CT), and various cultures of ETEC and Salmonella serotype Typhimurium in the porcine small intestine (Sus scrofa) were investigated. In anaesthetized pigs, jejunal tied-off loops were instilled with 5-HT, LT, CT, various
Marie Louise Gr°ndahl; Martin Andreas Unmack; Helga Berglind Ragnarsd¾ttir; Mark Berner Hansen; John Elmerdahl Olsen; Erik Skadhauge
Enhancement of the anti-tumour effects of the antivascular agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA) by combination with 5-hydroxytryptamine and bioreductive drugs
The tumour blood flow inhibitor 5,6-dimethylxanthenone-4-acetic acid (DMXAA) causes dramatic haemorrhagic necrosis in murine tumours, but activity is seen only at doses close to the toxic limit. This study investigates two approaches for increasing the therapeutic ratio of DMXAA. The first approach combines DMXAA with a second tumour blood flow inhibitor, 5-hydroxytryptamine (5-HT). Co-administration of 5-HT (700 micromol kg(-1)) to
CJ Lash; AE Li; M Rutland; BC Baguley; LJ Zwi; WR Wilson
Dorsal raphe neurons signal reward through 5-HT and glutamate.
The dorsal raphe nucleus (DRN) in the midbrain is a key center for serotonin (5-hydroxytryptamine; 5-HT)-expressing neurons. Serotonergic neurons in the DRN have been theorized to encode punishment by opposing the reward signaling of dopamine neurons. Here, we show that DRN neurons encode reward, but not punishment, through 5-HT and glutamate. Optogenetic stimulation of DRN Pet-1 neurons reinforces mice to explore the stimulation-coupled spatial region, shifts sucrose preference, drives optical self-stimulation, and directs sensory discrimination learning. DRN Pet-1 neurons increase their firing activity during reward tasks, and this activation can be used to rapidly change neuronal activity patterns in the cortex. Although DRN Pet-1 neurons are often associated with 5-HT, they also release glutamate, and both neurotransmitters contribute to reward signaling. These experiments demonstrate the ability of DRN neurons to organize reward behaviors and might provide insights into the underlying mechanisms of learning facilitation and anhedonia treatment. PMID:24656254
Liu, Zhixiang; Zhou, Jingfeng; Li, Yi; Hu, Fei; Lu, Yao; Ma, Ming; Feng, Qiru; Zhang, Ju-En; Wang, Daqing; Zeng, Jiawei; Bao, Junhong; Kim, Ji-Young; Chen, Zhou-Feng; El Mestikawy, Salah; Luo, Minmin
Binding interactions of antagonists with 5-hydroxytryptamine3A receptor models.
Homology modeling was performed on the N-terminal extracellular regions of human, mouse, and guinea pig 5-hydroxytryptamine type 3A receptors (5-HT3R) based on the 24% sequence homology with and on the crystal structure of the snail acetylcholine binding protein (AChBP). Docking of 5-HT3 antagonists granisetron, tropisetron, ondansetron, dolasetron ('setrons), and (+)-tubocurarine suggests an aromatic binding cleft behind a hydrophilic vestibule. Several intra- and interface interactions, H-bonds, and salt bridges stabilize the pentameric structure and the binding cleft. The planar rings of antagonists are intercalated between aromatic side-chains (W183-Y234, Y143-Y153). S227 donates H-bonds to the carbonyl groups of 'setrons. The tertiary ammonium ions interact with E236, N128 or E129, and/or W90 (cation-pi interaction). This offers a molecular explanation of the pharmacophore models of 5-HT3R antagonists. Docking artifacts suggest some ambiguities in the binding loops A and C of the 5-HT3AR models. Lower potencies of (+)-tubocurarine for human, and those of tropisetron for guinea pig 5-HT3ARs can be attributed to steric differences of I/S230 in the binding cleft and to distinct binding interactions with E229 and S227, respectively. Ligand binding interferes with crucial intra- and interface interactions along the binding cleft. PMID:14626451
Maksay, Gßbor; Bikßdi, Zsolt; Simonyi, Mikl¾s
Atypical neuroleptics enhance histamine turnover in brain via 5-Hydroxytryptamine2A receptor blockade.
Clozapine and olanzapine behave as weak H3-receptor antagonists in vitro with Ki values around 1 and 50 microM, respectively. Despite these modest apparent affinities, both compounds given orally to mice, nearly doubled steady-state tele-methylhistamine levels in brain, with ED50 values as low as 1 and 3 mg/kg, respectively, an effect comparable to those of potent H3-receptor antagonists. This effect corresponded to an enhancement of histamine turnover rate from 45 to 73 ng/g/h as measured in the case of olanzapine using the pargyline test. Other antipsychotics displaying, such as clozapine and olanzapine, high 5-hydroxytryptamine (5-HT)2A receptor antagonist potency, i.e., risperidone, thioridazine, seroquel, and iloperidone, also enhanced markedly tele-methylhistamine levels. This effect was 1) additive with that of a pure H3-receptor antagonist, ciproxifan, 2) mimicked by a 5-HT2A receptor antagonist, ketanserin, 3) reversed by a 5-HT2A receptor agonist, DOI, 4) not shared by antipsychotics with low affinity for the 5-HT2A receptor, i.e., haloperidol, sulpiride, raclopride, or remoxipride that, on the contrary, tended to reduce tele-methylhistamine levels. We conclude that in contrast to "typical" antipsychotics, "atypical" antipsychotics stimulate histamine neuron activity via blockade of the 5-HT2A receptor in vivo. This effect does not appear to account for their reduced extrapyramidal side-effects but may underlie their pro-cognitive properties. PMID:9918563
Morisset, S; Sahm, U G; Traiffort, E; Tardivel-Lacombe, J; Arrang, J M; Schwartz, J C
Elemental maps in human allantochorial placental vessels cells. 3. 5-hydroxytryptamine effects.
The membrane potential, a regulator of vascular tone, is a function of the physiological activities of ionic channels (particularly, K+ and Ca2+ channels in these cells). These channels regulate the ionic distribution into these cells. Micro-particule induced X-ray emission (PIXE) analysis was applied to determine the ionic composition of vascular smooth muscle cells (VSMCs) and of vascular endothelial cells (VECs) in the placental human allantochorial vessels in a physiological medium (Hanks'solution) modified by the addition of a chemical stimulus: 5-hydroxytryptamine (5-HT), an activator of the voltage-sensitive Ca2+ channels. In VSMCs (media layer), the addition of 5-HT induced no modification of the Na, K, Cl, P, S and Ca concentrations but increased Mg concentration. In endothelium (VECs) 5-HT addition implicated an increase of the K, S, Ca concentrations, the concentration of the other ions remained constant. In VECs, Ca and K increase is due to open of L-type voltage-dependent Ca2+ channels and of K(Ca) channels. 5-HT induces also a secretion of endothelium hyperpolarizing factors which implicate decrease of [Ca2+]i in VSMCs opposite to a direct increase by 5-HT. Increase in [Mg2+]i may be due to activation of the Ca/Mg exchanger. PMID:12899438
Guiet-Bara, A; Michelet-Habchi, C; Barberet, Ph; Dutta, R K; Moretto, Ph; Bara, M
Effect of Restraint Stress and Anxiolytics on 5HT Turnover in Rat Brain
In male Tuck AHA rats, restraint stress had no effect on 5-hydroxytryptamine (5-HT) levels in the frontal cortex, amygdala, hypothalamus and hippocampus, but produced a significant increase in 5-hydroxyindoleacetic acid (5-HIAA) levels in the amygdala after 120 and 180 min, and in the hypothalamus after 180 min. This apparent increase in turnover was not paralleled by a concomitant increase in
Stephen N. Mitchell; Patrick J. Thomas
Dual dopamine¢5HT releasers: potential treatment agents for cocaine addiction
Biogenic amine transporters (BATs) are integral membrane proteins that translocate biogenic amine neurotransmitters (norepinephrine, dopamine (DA) and 5-hydroxytryptamine (5-HT)) across cell mem- branes. BATs are the principal sites of action for many psychotropic drugs, including abused stimulants such as cocaine and methamphetamine. Preclinical and human data demonstrate that withdrawal from long-term cocaine administration produces a dual deficit of synap- tic
Richard B. Rothman; Bruce E. Blough; Michael H. Baumann
Is the 5HT 7 receptor involved in the pathogenesis and prophylactic treatment of migraine?
The mechanisms underlying the pathogenesis of migraine and their possible association with serotonin (5-hydroxytryptamine; 5-HT) have not yet been elucidated. One of the major obstacles in achieving this goal is the lack of information on the mechanisms by which the monoamine could possibly trigger and\\/or modulate the basic pathophysiological features of the condition, that is, cranial vasodilatation and neurogenic inflammation.
Josķ A. Terr¾n
Simultaneous measurement of adenosine, dopamine, acetylcholine and 5-hydroxytryptamine in cerebral mice microdialysis samples by LC-ESI-MS/MS.
A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed for the simultaneous measurement of adenosine (ADE), dopamine (DA), acetylcholine (ACh) and 5-hydroxytryptamine (5-HT) in mouse brain microdialysates. High method sensitivity (LLOQ of 0.05nM) was achieved by optimization of chromatographic and mass spectrometric parameters. The method was fully validated for its sensitivity, selectivity, matrix effect and stability. The LC-MS/MS method was successfully applied to evaluate the effect of the systemic administration of cocaine or amphetamine on the extracellular levels of ADE, DA, ACh and 5-HT in the mouse nucleus accumbens by microdialysis. PMID:22921776
Cannazza, Giuseppe; Carrozzo, Marina M; Cazzato, Addolorata S; Bretis, Irina M; Troisi, Luigino; Parenti, Carlo; Braghiroli, Daniela; Guiducci, Stefania; Zoli, Michele
5-HT systems: emergent targets for memory formation and memory alterations.
Drugs acting through 5-hydroxytryptamine (serotonin or 5-HT) systems modulate memory and its alterations, although the mechanisms involved are poorly understood. 5-HT drugs may present promnesic and/or antiamnesic (or even being amnesic) effects. Key questions regarding 5-HT markers include whether receptors directly or indirectly participate and/or contribute to the physiological and pharmacological basis of memory and its pathogenesis; hence, the major aim of this article was to examine recent advances in emergent targets of the 5-HT systems for memory formation and memory alterations. Recent reviews and findings are summarized, mainly in the context of the growing notion of memory deficits in brain disorders (e.g., posttraumatic stress disorder, mild cognitive impairment, consumption of drugs, poststroke cognitive dysfunctions, schizophrenia, Parkinson disease, and infection-induced memory impairments). Mainly, mammalian and (some) human data were the focus. At least agonists and antagonists for 5-HT1A/1B, 5-HT2A/2B/2C, 5-HT3, 5-HT4, 5-HT6, and 5-HT7 receptors as well as serotonin uptake inhibitors seem to have a promnesic and/or antiamnesic effect in different conditions and 5-HT markers seem to be associated to neural changes. Available evidence offers clues about the possibilities, but the exact mechanisms remain unclear. For instance, 5-HT transporter expression seems to be a reliable neural marker related to memory mechanisms and its alterations. PMID:24259245
Meneses, Alfredo
Neuronal localization of the 5-HT2 receptor family in the amygdaloid complex
The amygdaloid complex (or amygdala), a heterogeneous structure located in the medial portion of the temporal lobe, is composed of deep, superficial, and ōremainingö nuclei. This structure is involved in the generation of emotional behavior, in the formation of emotional memories and in the modulation of the consolidation of explicit memories for emotionally arousing events. The serotoninergic fibers originating in the dorsal and medial raphe nuclei are critically involved in amygdalar functions. Serotonin (5-hydroxytryptamine, 5-HT) regulates amygdalar activity through the activation of the 5-HT2 receptor family, which includes three receptor subtypes: 5-HT2A, 5-HT2B, and 5-HT2C. The distribution and the functional activity of the 5-HT2 receptor family has been studied more extensively than that of the 5-HT2A receptor subtypes, especially in the deep nuclei. In these nuclei, the 5-HT2A receptor is expressed on both pyramidal and non-pyramidal neurons, and could play a critical role in the formation of emotional memories. However, the exact role of the 5-HT2A receptor subtypes, as well as that of the 5-HT2B and 5-HT2C receptor subtypes, in the modulation of the amygdalar microcircuits requires additional study. The present review reports data concerning the distribution and the functional roles of the 5-HT2 receptor family in the amygdala.
Bombardi, Cristiano
Brain tissue transplanted to the anterior chamber of the eye: 2. Fluorescence histochemistry of immature catecholamine and 5-hydroxytryptamine neurons innervating the rat vas deferens
Small pieces of the wall of the rat vas deferens were homologously transplanted to the anterior chamber of the eye together with small pieces of embryonic brain stem containing either developing noradrenaline (NA) cells of the locus coeruleus or 5-hydroxytryptamine (5-HT) neurons of the developing raphe system. The eyes of the recipients were sympathetically denervated. The double transplants became rapidly
Lars Olson; ┼ke Seiger
Effect of 5-hydroxytryptamine on sodium- and potassium-dependent adenosine triphosphatase and its reactivity toward ouabain.
Activity of vertebrate Na+,K+-ATPase was inhibited by 5-hydroxytryptamine. Inhibition was reversible, and activity could be restored by dilution of 5-hydroxytryptamine (5HT). The ability of indole derivatives to inhibit depended on the presence of a net charge on the third atom of the indole C-3 side chain. Indoles with a net positive charge, such as 5HT, were stronger inhibitors than those with a net negative charge. Derivatives with a net charge of zero were not inhibitors. The ability of indole derivatives to inhibit Na+, K+-ATPase activity decreased in the order 5HT > tryptamine > tryptophanamide > tryptophol > N-acetyl-5-methoxytryptamine > indole-3-acetic acid. Trp did not inhibit either ATPase or pNPPase activity. Charged indole derivatives also inhibited the pNPPase activity of Na+,K+-ATPase. 5HT and tryptophanamide were stronger inhibitors of pNPPase activity than indole-3-acetic acid. Binding of [3H]ouabain was inhibited by 5HT and tryptophanamide. Trp did not inhibit [3H]ouabain binding. The near equilibrium level of [3H]-ouabain binding in the presence of ATP, Mg2+, and Na+ was decreased by 5HT in the manner characteristic of a competitive inhibitor. Enzyme-bound [3H]ouabain could be displaced by 5HT. 5HT was a complex mixed inhibitor of K+ with interactions at two sites, Tris was a competitive inhibitor with interactions at three sites, and ouabain was a simple noncompetitive inhibitor. The data are explained through a model indole binding site containing oppositely charged residues. PMID:8990266
Stepp, L R; Novakoski, M A
Mechanism of the 5-hydroxytryptamine 2A receptor-mediated facilitation of synaptic activity in prefrontal cortex.
Classic hallucinogens such as lysergic acid diethylamide are thought to elicit their psychotropic actions via serotonin receptors of the 5-hydroxytryptamine 2A subtype (5-HT(2A)R). One likely site for these effects is the prefrontal cortex (PFC). Previous studies have shown that activation of 5-HT(2A)Rs in this region results in a robust increase in spontaneous glutamatergic synaptic activity, and these results have led to the widely held idea that hallucinogens elicit their effect by modulating synaptic transmission within the PFC. Here, we combine cellular and molecular biological approaches, including single-cell 5-HT(2A)Rs inactivation and 5-HT(2A)R rescue over a 5-HT(2A)R knockout genetic background, to distinguish between competing hypotheses accounting for these effects. The results from these experiments do not support the idea that 5-HT(2A)Rs elicit the release of an excitatory retrograde messenger nor that they activate thalamocortical afferents, the two dominant hypotheses. Rather, they suggest that 5-HT(2A)Rs facilitate intrinsic networks within the PFC. Consistent with this idea, we locate a discrete subpopulation of pyramidal cells that is strongly excited by 5-HT(2A)R activation. PMID:17535909
Bķ'que, Jean-Claude; Imad, Mays; Mladenovic, Ljiljana; Gingrich, Jay A; Andrade, Rodrigo
Cinitapride protects against ethanol-induced gastric mucosal injury in rats: role of 5-hydroxytryptamine, prostaglandins and sulfhydryl compounds.
This study was designed to determine the gastroprotective properties of cinitapride (CNT), a novel prokinetic benzamide derivative agonist of 5-HT4 and 5-HT1 receptors and 5-HT2 antagonist, on mucosal injury produced by 50% (v/v) ethanol. Results were compared with those for 5-hydroxytryptamine (5-HT: 10 mg kg-1). The possible involvements of gastric mucus secretion, endogenous prostaglandins (PGs) and sulfhydryl compounds (SH) in the protection mediated by CNT were also examined. Intraperitoneal administration of CNT (0.50 and 1 mg kg-1), 30 min before ethanol, significantly prevented gastric ulceration and increased the hexosamine content of gastric mucus. CNT (1 mg kg-1) also produced a significant increase in gastric mucosal levels of PGE2, but did not induce any significant changes in SH values. On the contrary, pretreatment with 5-HT worsened ethanol-induced erosions, however, did not affect gastric mucus secretion, glycoprotein content or PGE2 levels, although the non-protein SH fraction was significantly decreased. The present results demonstrate that the gastroprotective effects of CNT could be partly explained by a complex PG dependent mechanism. We suggest that 5-HT dependent mechanisms through 5-HT2 receptor blockade and 5-HT1 receptor activation could be also involved. PMID:9211565
Alarc¾n-de-la-Lastra Romero, C; L¾pez, A; MartĒn, M J; la Casa, C; Motilva, V
Vortioxetine, but not escitalopram or duloxetine, reverses memory impairment induced by central 5-HT depletion in rats: evidence for direct 5-HT receptor modulation.
Depressed patients suffer from cognitive dysfunction, including memory deficits. Acute serotonin (5-HT) depletion impairs memory and mood in vulnerable patients. The investigational multimodal acting antidepressant vortioxetine is a 5-HT3, 5-HT7 and 5-HT1D receptor antagonist, 5-HT1B receptor partial agonist, 5-HT1A receptor agonist and 5-HT transporter (SERT) inhibitor that enhances memory in normal rats in novel object recognition (NOR) and conditioned fear (M°rk et al., 2013). We hypothesized that vortioxetine's 5-HT receptor mechanisms are involved in its memory effects, and therefore investigated these effects in 5-HT depleted rats. Four injections of the irreversible tryptophan hydroxylase inhibitor 4-chloro-dl-phenylalanine methyl ester hydrochloride (PCPA, 86mg/kg, s.c.) induced 5-HT depletion, as measured in hippocampal homogenate and microdialysate. The effects of acute challenge with vortioxetine or the 5-HT releaser fenfluramine on extracellular 5-HT were measured in PCPA-treated and control rats. PCPA's effects on NOR and spontaneous alternation (SA) performance were assessed along with the effects of acute treatment with 5-hydroxy-l-tryptophan (5-HTP), vortioxetine, the selective 5-HT reuptake inhibitor escitalopram, or the 5-HT norepinephrine reuptake inhibitor duloxetine. SERT occupancies were estimated by ex vivo autoradiography. PCPA depleted central 5-HT by >90% in tissue and microdialysate, and impaired NOR and SA performance. Restoring central 5-HT with 5-HTP reversed these deficits. At similar SERT occupancies (>90%) vortioxetine, but not escitalopram or duloxetine, restored memory performance. Acute fenfluramine significantly increased extracellular 5-HT in control and PCPA-treated rats, while vortioxetine did so only in control rats. Thus, vortioxetine restores 5-HT depletion impaired memory performance in rats through one or more of its receptor activities. PMID:24284262
Jensen, Jesper Born°; du Jardin, Kristian Gaarn; Song, Dekun; Budac, David; Smagin, Gennady; Sanchez, Connie; Pehrson, Alan Lars
MDL 72222: a potent and highly selective antagonist at neuronal 5-hydroxytryptamine receptors.
The properties of MDL 72222 (1 alpha H, 3 alpha, 5 alpha H-tropan-3-yl-3,5-dichlorobenzoate), a novel compound with potent and selective blocking actions at certain excitatory 5-hydroxytryptamine (5-HT) receptors on mammalian peripheral neurones, are described. On the rabbit isolated heart, MDL 72222 was a potent antagonist of responses mediated through the receptors for 5-HT present on the terminal sympathetic fibres. The threshold for antagonism was approximately 0.1 nM and the negative logarithm of the molar concentration of MDL 72222 which reduced the chronotropic response of the isolated rabbit heart to twice an ED50 of 5-HT to that of the ED50 was 9.27. MDL 72222 was also highly selective since responses to the nicotine receptor agonist, dimethylphenylpiperazinum iodine (DMPP), were inhibited only at concentrations more than 1000 times those necessary to inhibit 5-HT. In the anaesthetised rat, MDL 72222 produced marked blockade of the Bezold-Jarisch effect of 5-HT. Again, inhibition was selective since much higher doses of MDL 72222 failed to alter the response to electrical stimulation of the efferent vagus nerves. In contrast, MDL 72222 proved only a weak and essentially non-selective antagonist of responses mediated by the 5-HT M-receptor present on the cholinergic nerves of the guinea-pig ileum. MDL 72222 does not block smooth muscle contractile responses elicited by oxytocin or mediated through 5-HT D-receptors, muscarinic or nicotinic cholinoceptors or histamine H1-receptors except at relatively high concentrations.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6472484
Fozard, J R
Interaction between picrotoxin and 5-hydroxytryptamine in the superior cervical ganglion of the cat
1. Electrophysiological techniques were utilized to study the actions of 5-hydroxytryptamine (5-HT) and picrotoxin on the superior cervical ganglion of the cat. 2. The intra-arterial administration of 5-HT to the ganglion elicited both depressant and excitatory actions. In low doses (0Ę01-0Ę5 ?g) the amine produced a depression of ganglionic transmission. In larger doses (2-50 ?g) it produced an excitation of ganglion cells (early discharge) and an initial enhancement of transmission, which was followed by depression. Picrotoxin (25-500 ?g, i.a.) blocked the initial excitatory effects of 5-HT but did not block the depression. Picrotoxin did not antagonize the excitatory actions of injected cholinomimetic agents or potassium chloride. 3. In ganglia conditioned by repetitive stimulation of the preganglionic nerve (30 Hz for 30 s) 5-HT also elicited a late-occurring and very prolonged discharge on certain postganglionic nerves (`spinal') but not on others (external carotid). The late discharge was only partially depressed by picrotoxin. 4. Recordings from the surface of the superior cervical ganglion revealed that 5-HT produced three types of ganglionic potentials: (1) an initial transient depolarization which coincided with the early discharge, (2) a late-occurring, prolonged depolarization which coincided with the late discharge, and (3) a hyperpolarization which in some experiments accompanied the depression of transmission. The late depolarization and hyperpolarization were not observed in every experiment. Picrotoxin (25-500 ?g) blocked the initial depolarization, but did not block the late depolarization or the hyperpolarization. 5. It is concluded the 5-HT can produce three distinct responses in the superior cervical ganglion: a depressant effect and two types of excitation. It seems likely that depression and excitation occur via the activation of different receptors, since picrotoxin selectively blocks the latter. The finding that picrotoxin is a 5-HT antagonist in peripheral ganglia raises the possibility that picrotoxin might also influence tryptaminergic mechanisms in the central nervous system.
de Groat, W. C.; Lalley, P. M.
Oestradiol modulation of serotonin reuptake transporter and serotonin metabolism in the brain of monkeys.
Serotonin (5-hydroxytryptamine; 5-HT) is an important brain neurotransmitter that is implicated in mental and neurodegenerative diseases and is modulated by ovarian hormones. Nevertheless, the effect of oestrogens on 5-HT neurotransmission in the primate caudate nucleus, putamen and nucleus accumbens, which are major components of the basal ganglia, and the anterior cerebral cortex, mainly the frontal and cingulate gyrus, is not well documented. The present study evaluated 5-HT reuptake transporter (SERT) and 5-HT metabolism in these brain regions in response to 1-month treatment with 17?-oestradiol in short-term (1 month) ovariectomised (OVX) monkeys (Macaca fascicularis). SERT-specific binding was measured by autoradiography using the radioligand [│H]citalopram. Biogenic amine concentrations were quantified by high-performance liquid chromatography. 17?-Oestradiol increased SERT in the superior frontal cortex and in the anterior cingulate cortex, in the nucleus accumbens, and in subregions of the caudate nucleus of OVX monkeys. 17?-Oestradiol left [│H]citalopram-specific binding unchanged in the putamen, as well as the dorsal and medial raphe nucleus. 17?-Oestradiol treatment decreased striatal concentrations of the precursor of 5-HT, 5-hydroxytryptophan, and increased 5-HT, dopamine and 3-methoxytyramine concentrations in the nucleus accumbens, caudate nucleus and putamen, whereas the concentrations of the metabolites 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid and homovanillic acid remained unchanged. No effect of 17?-oestradiol treatment was observed for biogenic amine concentrations in the cortical regions. A significant positive correlation was observed between [│H]citalopram-specific binding and 5-HT concentrations in the caudate nucleus, putamen and nucleus accumbens, suggesting their link. These results have translational value for women with low oestrogen, such as those in surgical menopause or perimenopause. PMID:23414342
Sßnchez, M G; Morissette, M; Di Paolo, T
Antidepressant-like activity of 5HT 1A agonists measured with the forced swim test
This study examined the abilities of 5-hydroxytryptamine (5-HT) agonists with varying selectivity for different subtypes of 5-HT receptors to produce antidepressant-like behavioral effects in the forced swim test in rats. The 5-HT1A agonists 8-OH-DPAT (0.125¢1.0 mg\\/kg, SC) and tandospirone (SM-3997) (5¢20 mg\\/kg, SC) both produced dose-related decreases in immobility time following subchronic treatment in rats. These effects were similar to
Scott Wieland; Irwin Lucki
Spatial memory deficits following stimulation of hippocampal 5HT 1B receptors in the rat
In this study we examined a possible contribution of serotonin (5-hydroxytryptamine, 5-HT) to spatial memory performance in the rat. Rats were trained to run in a radial maze in a manner that involved two kinds of memory function, i.e. working memory and reference memory. They received intrahippocampal microinjections of a 5-HT1A [8-hydroxy-2-(di-n-propylamino)tetralin or 8-OH-DPAT], or a 5-HT1B [3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo[3,2-b]pyrid-5-one or CP-93,129
Marie-Christine Buhot; Sarat K. Patra; Sa'd Na'li
Serotonin (5HT7) Receptor-Stimulated Activation of cAMP-PKA Pathway in Bovine Corneal Epithelial and Endothelial Cells
Background: 5-Hydroxytryptamine (5-HT; serotonin) is a major neurotransmitter, and its receptors are found throughout the whole body. The 5-HT7 receptor subtype was detected in human corneal epithelial and endothelial cells and found to be functionally active in a corneal epithelial cell line. The aim of the present study was to demonstrate that native bovine corneal epithelial and endothelial cells express
Matthias Grueb; Jens Martin Rohrbach; Torsten Schlote; Joerg Mielke
Distribution of cells responsive to 5-HT6 receptor antagonist-induced hypophagia
The central 5-hydroxytryptamine (5-HT; serotonin) system is well established as an important regulator of appetite and continues to remain a focus of obesity research. While much emphasis has focussed on the 5-HT2C receptor (5-HT2CR) in 5-HT's anorectic effect, pharmacological manipulation of the 5-HT6 receptor (5-HT6R) also reduces appetite and body weight and may be amenable to obesity treatment. However, the neurological circuits that underlie 5-HT6R-induced hypophagia remain to be identified. Using c-fos immunoreactivity (FOS-IR) as a marker of neuronal activation, here we mapped the neuroanatomical targets activated by an anorectic dose of the 5-HT6R antagonist SB-399885 throughout the brain. Furthermore, we quantified SB-399855 activated cells within brain appetitive nuclei, the hypothalamus, dorsal raphe nucleus (DRN) and nucleus of the solitary tract (NTS). Our results reveal that 5-HT6R antagonist-induced hypophagia is associated with significantly increased neuronal activation in two nuclei with an established role in the central control of appetite, the paraventricular nucleus of the hypothalamus (PVH) and the NTS. In contrast, no changes in FOS-IR were observed between treatment groups within other hypothalamic nuclei or DRN. The data presented here provide a first insight into the neural circuitry underlying 5-HT6R antagonist-induced appetite suppression and highlight the PVH and NTS in the coordination of 5-HT6R hypophagia.
Garfield, Alastair S.; Burke, Luke K.; Shaw, Jill; Evans, Mark L.; Heisler, Lora K.
Effects of fluoxetine and buspirone on the panicolytic-like response induced by the activation of 5HT 1A and 5HT 2A receptors in the rat dorsal periaqueductal gray
RationaleĀĀAdministration of 5-hydroxytryptamine (5-HT)1A and 5-HT2A receptor agonists into the dorsal periaqueductal gray (DPAG) inhibits escape, a defensive behavior associated with panic\\u000a attacks. Long-term treatment with the antipanic compound imipramine enhances the DPAG 5-HT1A- and 5-HT2A-receptor-mediated inhibition of escape, implicating these receptors in the mode of action of panicolytic drugs.\\u000a \\u000a \\u000a \\u000a ObjectivesĀĀIn the present study, we investigated whether the inhibitory effect
ValquĒria Camin de Bortoli; Regina L·cia Nogueira; Hķlio Zangrossi Jr
Functional changes in cerebral 5-hydroxytryptamine metabolism in the mouse induced by anticonvulsant drugs.
1 Acute administration of clonazepam, diazepam, and diphenylhydantoin to mice elevated cerebral 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA); chronic administration had less effect. 2 Acute administration of clonazepam and diazepam but not diphenylhydantoin raised cerebral trytophan levels; chronic administration of clonazepam caused a smaller elevation of cerebral tryptophan but chronic administration of diazepam still caused a large rise in cerebral tryptophan. 3 Neither clonazepam nor diazepam caused induction of drug metabolizing enzymes on chronic administration but diphenylhydantoin had a marked effect. 4 These data suggest that the altered 5-HT metabolism caused by these compounds is unrelated to a common action on tryptophan levels, and that the reduced effect of clonazepam and diazepam on chronic administration cannot be attributed to increased metabolism of these compounds. 5 Clonazepam induced abnormal head movements in mice in a dose-dependent manner. Pretreatment of animals with tranylcypromine increased the intensity of movement, although pargyline was without effect. Similar effects were observed with diazepam and diphenylhydantoin, suggesting that the increase in cerebral 5-HT caused by these compounds is of functional significance in stimulating 5-HT receptors.
Chadwick, D; Gorrod, J W; Jenner, P; Marsden, C D; Reynolds, E H
GABAB-receptor mediated inhibition of potassium-evoked release of endogenous 5-hydroxytryptamine from mouse frontal cortex.
The effect of baclofen, the GABAB-agent, on the potassium-evoked release of endogenous 5-hydroxytryptamine (5-HT) from slices of mouse frontal cortex has been investigated. The release of endogenous 5-HT evoked by addition of K+ (35 mM) was inhibited by (+/-)-baclofen in a dose-dependent manner with an IC50 of 0.1 microM. Inhibition of K+-evoked release of 5-HT was produced by (+/-)- and (-)-baclofen but not (+)-baclofen. This action of the (-)-enantiomer was not altered by the presence of the (+)-enantiomer. Addition of GABA (0.1-10 microM) also induced a dose-dependent inhibition of 5-HT release. This effect was neither enhanced by flurazepam (1 microM) nor antagonized by bicuculline (10 microM). The progabide metabolite, 4-[( (4-chlorophenyl) (5-fluoro-2-hydroxyphenyl)methylene]amino)butyric acid (SL75.102) (1 microM) inhibited the K+-evoked release of 5-HT by 61%. These data suggest that baclofen is a potent inhibitor of the K+-evoked release of endogenous 5-HT from the cortex and further indicate that the release of 5-HT may be controlled by a GABAB-receptor located presynaptically.
Gray, J. A.; Green, A. R.
GABAB-receptor mediated inhibition of potassium-evoked release of endogenous 5-hydroxytryptamine from mouse frontal cortex.
The effect of baclofen, the GABAB-agent, on the potassium-evoked release of endogenous 5-hydroxytryptamine (5-HT) from slices of mouse frontal cortex has been investigated. The release of endogenous 5-HT evoked by addition of K+ (35 mM) was inhibited by (+/-)-baclofen in a dose-dependent manner with an IC50 of 0.1 microM. Inhibition of K+-evoked release of 5-HT was produced by (+/-)- and (-)-baclofen but not (+)-baclofen. This action of the (-)-enantiomer was not altered by the presence of the (+)-enantiomer. Addition of GABA (0.1-10 microM) also induced a dose-dependent inhibition of 5-HT release. This effect was neither enhanced by flurazepam (1 microM) nor antagonized by bicuculline (10 microM). The progabide metabolite, 4-[( (4-chlorophenyl) (5-fluoro-2-hydroxyphenyl)methylene]amino)butyric acid (SL75.102) (1 microM) inhibited the K+-evoked release of 5-HT by 61%. These data suggest that baclofen is a potent inhibitor of the K+-evoked release of endogenous 5-HT from the cortex and further indicate that the release of 5-HT may be controlled by a GABAB-receptor located presynaptically. PMID:3038240
Gray, J A; Green, A R
5HT 7 receptor subtype as a mediator of the serotonergic regulation of luteinizing hormone release in the zona incerta
5-Hydroxytryptamine (5-HT) and the 5-HT1A\\/7 receptor agonist (+)-8-hydroxy-2-(di-n-propylamino) tetralinHBr (8-OH-DPAT), injected into the zona incerta (an area in the dorsal hypothalamus) of the female rat, inhibit the release of luteinizing hormone (LH) and the effects of both are blocked by the 5-HT2\\/7 receptor antagonist, ritanserin. As both 8-OH-DPAT and ritanserin have moderate activity at the 5-HT7 receptor subtype, the possibility
Arif Siddiqui; Mahmoud Abu-Amara; Cyrielle Aldairy; James J. Hagan; Catherine Wilson
Practical access to four stereoisomers of naftidrofuryl and their binding affinity towards 5-hydroxytryptamine 2A receptor.
Naftidrofuryl oxalate (Praxilene«, 1) has been used for the treatment of intermittent claudication for more than 30 years. It selectively blocks vascular and platelet 5-hydroxytryptamine 2 (5-HT(2)) receptors. This drug is marketed as a mixture of four stereoisomers, and so far there is no individual biological evaluation on the single isomers. The purpose of this study is to provide an improved method for the preparation of all four stereoisomers of naftidrofuryl, and more importantly, to distinguish them in terms of their binding affinity to 5-hydroxytryptamine 2A (5-HT(2A)) receptor. The bioassay results revealed that the C-2S configuration of naftidrofuryl was crucial for the binding affinity with 5-HT(2A) receptor, and the C-2' configuration was less important for binding. In conclusion, our study may pave the way to develop single naftidrofuryl isomers with C-2S configuration as inhibitors of 5-HT(2A) receptor that have clinical significance as vasodilators and CNS agents. PMID:22516281
Hao, Jia; Chen, Bo; Yao, Yiwu; Hossain, Murad; Nagatomo, Takafumi; Yao, Hequan; Kong, Lingyi; Sun, Hongbin
Peptide YY3¢36 and 5-Hydroxytryptamine Mediate Emesis Induction by Trichothecene Deoxynivalenol (Vomitoxin)
Deoxynivalenol (DON, vomitoxin), a trichothecene mycotoxin produced by Fusarium sp. that frequently occurs in cereal grains, has been associated with human and animal food poisoning. Although a common hallmark of DON-induced toxicity is the rapid onset of emesis, the mechanisms for this adverse effect are not fully understood. Recently, our laboratory has demonstrated that the mink (Neovison vison) is a suitable small animal model for investigating trichothecene-induced emesis. The goal of this study was to use this model to determine the roles of two gut satiety hormones, peptide YY3¢36 (PYY3¢36) and cholecystokinin (CCK), and the neurotransmitter 5-hydroxytryptamine (5-HT) in DON-induced emesis. Following ip exposure to DON at 0.1 and 0.25mg/kg bw, emesis induction ensued within 15¢30min and then persisted up to 120min. Plasma DON measurement revealed that this emesis period correlated with the rapid distribution and clearance of the toxin. Significant elevations in both plasma PYY3¢36 (30¢60min) and 5-HT (60min) but not CCK were observed during emesis. Pretreatment with the neuropeptide Y2 receptor antagonist JNJ-31020028 attenuated DON- and PYY-induced emesis, whereas the CCK1 receptor antagonist devezapide did not alter DONÆs emetic effects. The 5-HT3 receptor antagonist granisetron completely suppressed induction of vomiting by DON and the 5-HT inducer cisplatin. Granisetron pretreatment also partially blocked PYY3¢36-induced emesis, suggesting a potential upstream role for this gut satiety hormone in 5-HT release. Taken together, the results suggest that both PYY3¢36 and 5-HT play contributory roles in DON-induced emesis.
Pestka, James J.
5-HT1-like receptors requiring functional cyclo-oxygenase and 5-HT2 receptors independent of cyclo-oxygenase mediate contraction of the human umbilical artery.
1. The interactions between 5-hydroxytryptamine (5-HT) and the antagonists ketanserin, methysergide and phentolamine were studied in isolated preparations of human umbilical artery (HUA) at physiological oxygen tension (Po2 approximately 15 mmHg) and at high PO2 (approximately 120 mmHg). 2. At physiological Po2 ketanserin, methysergide and phentolamine behaved as silent competitive antagonists of the 5-HT-induced contraction of HUA. pA2 values calculated by Schild analysis were 8.92, 8.52 and 6.37, respectively. 3. At high Po2, 5-HT-induced contractions were antagonised in a biphasic manner by ketanserin (0.1 microM); the response to low but not to high concentrations of 5-HT was resistant to blockade by ketanserin. The ketanserin-resistant component was abolished following cyclo-oxygenase inhibition by indomethacin (1 microM). 4. At high Po2, methysergide behaved as a partial agonist. Methysergide-induced contractions were inhibited but not abolished by indomethacin, and resistant to 5-HT2 receptor and alpha 1-adrenoceptor blockade. 5. At high Po2 the component of the response to 5-HT mediated by the ketanserin-resistant receptor was mimicked by the selective 5-HT1-like receptor agonist 5-carboxamidotryptamine (5-CT): 5-CT was 7 fold more potent than 5-HT. 6. At high Po2 the component of the response to 5-HT mediated by the ketanserin-resistant receptor was antagonised by phentolamine and the selective alpha 2-adrenoceptor antagonist Wy 26703. 7. These results suggest that (i) at physiological Po2 5-HT2 receptors almost exclusively mediate contractions induced by 5-HT, and (ii) at high Po2 the agonist potency order of 5-CT greater than 5-HT greater than methysergide suggests that ketanserin-resistant responses are mediated by 5-HT1-like receptors which require functional cyclo-oxygenase.
MacLennan, S. J.; Whittle, M. J.; McGrath, J. C.
5-Hydroxytryptamine receptor-mediated phosphoinositide hydrolysis in canine cultured tracheal smooth muscle cells.
1. 5-Hydroxytryptamine (5-HT) has been shown to induce contraction of tracheal smooth muscle. However, the mechanisms of action of 5-HT are not known. We therefore investigated the effects of 5-HT on phospholipase C (PLC)-mediated phosphoinositide (PI) hydrolysis and its regulation in canine cultured tracheal smooth muscle cells (TSMCs) labelled with [3H]-inositol. 5-HT-induced inositol phosphates (IPs) accumulation was time- and dose-dependent with a half-maximal response (EC50) and a maximal response at 0.38 +/- 0.05 and 10 microM, respectively. 2. Ketanserin and mianserin (10 and 100 nM), 5-HT2 receptor antagonists, were equipotent in blocking the 5-HT-induced IPs accumulation with pKB values of 8.46 and 8.21, respectively. In contrast, the dose-response curves of 5-HT-induced IPs accumulation were not shifted until the concentrations of NAN-190 and metoclopramide (5-HT1A and 5-HT3 receptor antagonists, respectively) were increased up to 10 microM. 3. Pretreatment of TSMCs with pertussis toxin or cholera toxin did not inhibit the 5-HT-induced IPs accumulation, but partially inhibited the AlF(4-)-induced IPs response. 4. Stimulation of IPs accumulation by 5-HT required the presence of external Ca2+ and was blocked by EGTA. The addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs directly stimulated IPs accumulation. A further Ca(2+)-dependent increase in IPs accumulation was obtained by inclusion of either guanosine 5'-O-(3-thiotriphoshate) (GTP gamma S) or 5-HT. The combination of GTP gamma S and 5-HT elicited an additive effect on IPs accumulation. 5. Treatment with phorbol 12-myristate 13-acetate (PMA, 1 microM, 30 min) abolished the 5-HT-induced IPs accumulation. The concentrations of PMA that gave a half-maximal and maximal inhibition of 5-HT-induced IPs accumulation were 2.2 +/- 0.4 nM and 1 microM, n = 3, respectively. The protein kinase C (PKC) activator, 4 alpha-phorbol 12,13-didecanoate, at 1 microM, did not influence this response. The inhibitory effect of PMA was reversed by staurosporine, a PKC inhibitor, suggesting that the inhibitory effect of PMA is mediated through the activation of PKC. 6. The site of this inhibition was further investigated by examining the effect of PMA on AlF(4-)-induced IPs accumulation in canine TSMCs. AlF(4-)-stimulated IPs accumulation was inhibited by PMA treatment, suggesting that the effect of PMA is distal to the 5-HT receptor.(ABSTRACT TRUNCATED AT 400 WORDS)
Yang, C. M.; Yo, Y. L.; Hsieh, J. T.; Ong, R.
Characterization of the 5-hydroxytryptamine receptor mediating the positive inotropic response in guinea-pig isolated left atria.
1. 5-Hydroxytryptamine (5-HT), in the presence of propranolol (1 microM), atropine (3 microM) and ketanserin (1 microM), induced a positive inotropic response of guinea-pig isolated electrically paced left atria (pEC50 = 7.52). The positive inotropic response was mimicked by alpha-methyl-5-HT (pEC50 = 7.26) and 5-carboxamidotryptamine (5-CT; pEC50 = 6.56) but not by sumatriptan or 1-(m-chlorophenyl) piperazine (m-CPP). 2. The 5-HT induced positive inotropic response was competitively antagonized by both mesulergine (pA2 = 7.68) and methiothepin (pA2 = 6.67). Methysergide was a surmountable antagonist at 3 nM producing a rightward shift in the 5-HT concentration-response curve giving an apparent pA2 = 9.2 with no significant reduction in the maximum. At higher concentrations, methysergide behaved as an insurmountable antagonist, significantly reducing the maximum response to 5-HT as well as producing rightward shifts in the 5-HT concentration-response curves. 3. The 5-HT-induced positive inotropic response was not antagonized by either tropisetron (10 microM) or yohimbine (10 microM). 4. The guinea-pig atrial 5-HT receptor does not satisfy the criteria for any of the currently recognised 5-HT receptor subtypes and appears to have some similarities to the atypical 5-HT receptors previously described in other peripheral tissues. PMID:8401929
Lattimer, N; Gupta, P; Rhodes, K F
Characterization of the 5-hydroxytryptamine receptor mediating the positive inotropic response in guinea-pig isolated left atria.
1. 5-Hydroxytryptamine (5-HT), in the presence of propranolol (1 microM), atropine (3 microM) and ketanserin (1 microM), induced a positive inotropic response of guinea-pig isolated electrically paced left atria (pEC50 = 7.52). The positive inotropic response was mimicked by alpha-methyl-5-HT (pEC50 = 7.26) and 5-carboxamidotryptamine (5-CT; pEC50 = 6.56) but not by sumatriptan or 1-(m-chlorophenyl) piperazine (m-CPP). 2. The 5-HT induced positive inotropic response was competitively antagonized by both mesulergine (pA2 = 7.68) and methiothepin (pA2 = 6.67). Methysergide was a surmountable antagonist at 3 nM producing a rightward shift in the 5-HT concentration-response curve giving an apparent pA2 = 9.2 with no significant reduction in the maximum. At higher concentrations, methysergide behaved as an insurmountable antagonist, significantly reducing the maximum response to 5-HT as well as producing rightward shifts in the 5-HT concentration-response curves. 3. The 5-HT-induced positive inotropic response was not antagonized by either tropisetron (10 microM) or yohimbine (10 microM). 4. The guinea-pig atrial 5-HT receptor does not satisfy the criteria for any of the currently recognised 5-HT receptor subtypes and appears to have some similarities to the atypical 5-HT receptors previously described in other peripheral tissues.
Lattimer, N.; Gupta, P.; Rhodes, K. F.
Mechanical stimulation activates G?q signaling pathways and 5-hydroxytryptamine release from human carcinoid BON cells
5-Hydroxytryptamine (5-HT) released from enterochromaffin cells activates secretory and peristaltic reflexes necessary for lubrication and propulsion of intestinal luminal contents. The aim of this study was to identify mechanosensitive intracellular signaling pathways that regulate 5-HT release. Human carcinoid BON cells displayed 5-HT immunoreactivity associated with granules dispersed throughout the cells or at the borders. Mechanical stimulation by rotational shaking released 5-HT from BON cells or from guinea pig jejunum during neural blockade with tetrodotoxin. In streptolysin O¢permeabilized cells, guanosine 5?-O- (2-thiodiphosphate) (GDP-?-S) and a synthetic peptide derived from the COOH terminus of G?q abolished mechanically evoked 5-HT release, while the NH2-terminal peptide did not. An antisense phosphorothioated oligonucleotide targeted to a unique sequence of G?q abolished mechanically evoked 5-HT release and reduced G?q protein levels without affecting the expression of G?11. Depletion and chelation of extracellular calcium did not alter mechanically evoked 5-HT release, whereas depletion of intracellular calcium stores by thapsigargin and chelation of intracellular calcium by 1,2-bis (o-Aminophenoxy) ethane-N,N,N?,N?-tetraacetic acid tetra (acetoxymethyl) ester (BAPTA-AM) reduced 5-HT release. Mechanically evoked 5-HT release was inhibited by somatostatin-14 in a concentration-dependent manner. The results suggest that mechanical stimulation of enterochromaffin-derived BON cells directly or indirectly stimulates a G protein¢coupled receptor that activates G?q, mobilizes intracellular calcium, and causes 5-HT release.
Kim, Minsoo; Javed, Najma H.; Yu, Jun-Ge; Christofi, Fievos; Cooke, Helen J.
Contributions of 5-HT Neurons to Respiratory Control: Neuromodulatory and Trophic Effects
Serotonin (5-hydroxytryptamine; 5-HT) is a neurotransmitter produced by a small number of neurons in the midbrain, pons and medulla. These neurons project widely throughout the neuraxis, where they release 5-HT and co-localized neuropeptides such as substance P (SP) and thyrotropin-releasing hormone (TRH). Each of these chemicals produce effects largely through G protein-coupled receptors, second messenger systems and subsequent neuromodulatory effects on target neurons. Emerging evidence suggests that 5-HT has additional modes of action during development and in adult mammals, including trophic effects (neurogenesis, cell differentiation, proliferation, migration and maturation) and influences on synaptic plasticity. Here, we discuss some of the neuromodulatory and trophic roles of 5-HT in general and in the context of respiratory control, as well as the regulation of release of modulatory neurotransmitters from 5-HT neurons. Future directions of study are also discussed.
Hodges, Matthew R.; Richerson, George B.
Analysis of the agonist activity of fenoldopam (SKF 82526) at the vascular 5-HT2 receptor.
1. The 5-HT2 receptor agonist activity of fenoldopam (SKF 82526) was characterized in the rabbit isolated aorta preparation. 2. Fenoldopam was an agonist at the vascular 5-HT2 receptor with lower affinity and efficacy than the naturally occurring agonist 5-hydroxytryptamine (5-HT). Fenoldopam had an affinity (pKA) of 5.84 +/- 0.04 and efficacy (tau) of 0.57 +/- 0.04, whereas 5-HT had a pKA of 6.65 +/- 0.12 and tau of 2.66 +/- 0.41. 3. The constrictor effects of fenoldopam and 5-HT were competitively antagonized by the 5-HT2 antagonist, ketanserin, with pKB values of 8.81 +/- 0.11 and 8.83 +/- 0.10 respectively. 4. Prior incubation with fenoldopam produced a concentration-related rightward shift of a subsequent 5-HT concentration-response curve. This inhibition was specific for 5-HT since constrictor responses to angiotensin II were unaffected. 5. This study indicates that the D1 receptor agonist, fenoldopam, acts as an agonist at the vascular 5-HT2 receptor, but with an affinity and efficacy less than that of the naturally occurring agonist, 5-HT.
Christie, M. I.; Harper, D.; Smith, G. W.
The love of a lifetime: 5-HT in the cardiovascular system.
Serotonin [5-hydroxytryptamine (5-HT)] is an amine made from the essential amino acid tryptophan. 5-HT serves numerous functions in the body, including mood, satiety, and gastrointestinal function. Less understood is the role 5-HT plays in the cardiovascular system, although 5-HT receptors have been localized to every important cardiovascular organ and 5-HT-induced changes in physiological function attributed to activation of these receptors. This manuscript relates a few scientific stories that test the idea that 5-HT is important to the control of normal vascular tone, more so in the hypertensive condition. Currently, our laboratory is faced with two different lines of experimentation from which one could draw vastly different conclusions as to the ability of 5-HT to modify endogenous vascular tone and blood pressure. Studies point to 5-HT being important in maintaining high blood pressure, but other studies solidly support the ability of 5-HT to reduce elevated blood pressure. This work underscores that our knowledge of the functions of 5-HT in the cardiovascular system is significantly incomplete. As such, this field is an exciting one in which to be, because there are superb questions to be asked. PMID:18753260
Watts, Stephanie W
The use of brain slices and dissociated neurones to explore the multiplicity of actions of 5HT in the central nervous system
The cellular actions of 5-hydroxytryptamine (5-HT) on adult and neonatal rat central neurones have been investigated in detail using a combination of in vitro slice and dissociated neurone preparations. Patch-clamp recordings from acutely dissociated adult rat dorsal raphe neurones confirm data obtained using conventional slice preparations that 5-HT activates an inwardly rectifying potassium channel through a 5-HT1A receptor leading to
P. M. Larkman; J. S. Kelly
Double-blind crossover study with dolasetron mesilate, a 5HT 3 receptor antagonist in cerebellar syndrome secondary to multiple sclerosis
Cerebellar syndrome is one of the most disabling developments in multiple sclerosis (MS). In neurodegenerative disorders, cerebellar syndrome is thought to be related to a neurochemical deficit of 5-hydroxytryptamine (5-HT). Previous studies found that a levorotatory form of 5-hydroxytryptophan, a 5-HT precursor, and ondansetron, a 5-HT 3 receptor antagonist, decreased cerebellar symptoms in FriedreichÆs ataxia and MS. We studied the
C. Monaca-Charley; T. Stojkovic; A. Duhamel; J. De Seze; D. Ferriby; P. Vermersch
5-hydroxytryptamine-mediated neurotransmission modulates spontaneous and vagal-evoked glutamate release in the nucleus of the solitary tract effect of uptake blockade.
The effect of blockade of either 5-hydroxytryptamine (5-HT)/serotonin transporter (SERT) with citalopram or the organic cation transporter 3 (OCT3)/plasma membrane monoamine transporter (PMAT) with decynium-22 (D-22) on spontaneous and evoked release of 5-HT in the nucleus tractus solitarius (NTS) was investigated in rat brainstem slices treated with gabazine. 5-HT release was measured indirectly by changes in the frequency and amplitude of glutamatergic miniature excitatory postsynaptic currents (mEPSCs) [in the presence of tetrodotoxin (TTX)] and evoked EPSCs. Blockade of 5-HT3 receptors with granisetron reduced, whereas the 5-HT3 agonist phenylbiguanide increased, the frequency of mEPSCs. 5-HT decreased mEPSC frequency at low concentrations and increased frequency at high concentrations. This inhibition was blocked by the 5-HT1A antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY-100635), which was ineffective on its own, whereas the excitation was reversed by granisetron. The addition of citalopram or D-22 caused inhibition, which was prevented by 5-HT1A blockade. Thus, in the NTS, the spontaneous release of 5-HT is able to activate 5-HT3 receptors, but not 5-HT1A receptors, as the release in their vicinity is removed by uptake. The ineffectiveness of corticosterone suggests that the low-affinity, high-capacity transporter is PMAT, not OCT3. For evoked 5-HT release, only D-22 caused an increase in the amplitude of EPSCs, with a decrease in the paired pulse ratio, and increased the number of spontaneous EPSCs after 20-Hz stimulation. Thus, for the evoked release of 5-HT, the low-affinity, high-capacity transporter PMAT, but not 5-HT transporter (5-HTT)/SERT, is important in the regulation of changes in 5-HT extracellular concentration. PMID:24618127
Hosford, Patrick S; Mifflin, Steve W; Ramage, Andrew G
The 5-HT4 receptor agonist, tegaserod, is a potent 5-HT2B receptor antagonist in vitro and in vivo
Tegaserod (Zelnorm«) is a potent 5-hydroxytryptamine4 (5-HT4) receptor agonist with clinical efficacy in disorders associated with reduced gastrointestinal motility and transit. The present study investigated the interaction of tegaserod with 5-HT2 receptors, and compared its potency in this respect to its 5-HT4 receptor agonist activity. Tegaserod had significant binding affinity for human recombinant 5-HT2A, 5-HT2B and 5-HT2C receptors (pKi=7.5, 8.4 and 7.0, respectively). The 5-HT2B receptor-binding affinity of tegaserod was identical to that at human recombinant 5-HT4(c) receptors (mean pKi=8.4) in human embryonic kidney-293 (HEK-293) cells stably transfected with the human 5-HT4(c) receptor. Tegaserod (0.1¢3 ?M) inhibited 5-HT-mediated contraction of the rat isolated stomach fundus potently (pA2=8.3), consistent with 5-HT2B receptor antagonist activity. Tegaserod produced, with similar potency, an elevation of adenosine 3?,5? cyclic monophosphate in HEK-293 cells stably transfected with the human 5-HT4(c) receptor (mean pEC50=8.6), as well as 5-HT4 receptor-mediated relaxation of the rat isolated oesophagus (mean pEC50=8.2) and contraction of the guinea-pig isolated colon (mean pEC50=8.3). Following subcutaneous administration, tegaserod (0.3 or 1 mg kg?1) inhibited contractions of the stomach fundus in anaesthetized rats in response to intravenous dosing of ?-methyl 5-HT (0.03 mg kg?1) and BW 723C86 (0.3 mg kg?1), selective 5-HT2B receptor agonists. At similar doses, tegaserod (1 and 3 mg kg?1 subcutaneously) evoked a 5-HT4 receptor-mediated increase in colonic transit in conscious guinea-pigs. The data from this study indicate that tegaserod antagonizes 5-HT2B receptors at concentrations similar to those that activate 5-HT4 receptors. It remains to be determined whether this 5-HT2B receptor antagonist activity of tegaserod contributes to its clinical profile.
Beattie, D T; Smith, J A M; Marquess, D; Vickery, R G; Armstrong, S R; Pulido-Rios, T; McCullough, J L; Sandlund, C; Richardson, C; Mai, N; Humphrey, P P A
5-Hydroxytryptamine receptors of visceral primary afferent neurones on rabbit nodose ganglia
1. The electrophysiological characteristics of 5-hydroxytryptamine (5-HT) receptors distributed on visceral primary afferent neurones (the nodose ganglion cells of the vagus) in rabbits were investigated with intracellular recording and voltage-clamp techniques. 2. In response to 5-HT applied by superfusion (? 10 ?m) or by ionophoresis (? 5 nA, 50 msec), the majority of type C neurones (mean axonal conduction velocity: 0Ę83▒0Ę25 m/sec) showed a rapid depolarization of 20-30 mV in amplitude which was followed by a hyperpolarization of a few millivolts. Both the initial depolarization and afterhyperpolarization were associated with a reduction in membrane resistance. 3. Type A neurones (mean axonal conduction velocity: 7Ę7▒0Ę4 m/sec) did not show any significant alterations in membrane potential and resistance during or after application of 5-HT. 4. The initial depolarization induced by 5-HT was abolished by Na+-free Krebs solution and showed a reduction of a few millivolts in K+-free or Ca2+-free Krebs solution. The response in normal Krebs solution was reversed at a membrane potential level of +7Ę3▒1Ę1 mV. 5. The afterhyperpolarization disappeared in Na+-free or Ca2+-free Krebs solution, while it was markedly enhanced in K+-free Krebs solution. The response in normal Krebs solution reversed at a membrane potential of -88Ę7▒0Ę8 mV, and was abolished at membrane potentials more positive than -20 mV. 6. Unlike 5-HT voltage responses, which were biphasic in the majority of neurones examined, 5-HT induced currents were usually monophasic when recorded at holding membrane levels ranging from -80 to +50 mV. The reversal potential of the inward current was +7Ę5▒0Ę8 mV which was in good agreement with the reversal level for 5-HT-induced depolarizations. The reversal potentials for inward currents which were obtained at various concentrations of Na+ or K+ corresponded to the theoretical values calculated by the equivalent circuit equation. 7. These results suggest that the initial depolarization induced by 5-HT is due mainly to simultaneous increases in Na+ and K+ conductances, while the afterhyperpolarization is brought about by an increase of K+ conductance which is triggered by a voltage-dependent influx of Na+ and Ca2+. 8. The mean value for the `limiting slope' of conductance change vs. 5-HT concentration and the slope of 5-HT current vs. 5-HT concentration obtained by superfusion of 5-HT, were in good agreement, 1Ę84▒0Ę26 and 1Ę88▒0Ę31, respectively. On the other hand, the mean Hill coefficient obtained from the doseŚresponse curves for the inward current induced by ionophoresis was 2Ę51▒0Ę14. 9. Tetrodotoxin (0Ę2 ?m) blocked the soma action potential completely, but did not show any effect on 5-HT-induced responses. 10. (+)-Lysergic acid diethylamide and methysergide (1-100 ?m) had no depressant effect on the 5-HT-induced depolarization. 11. (+)-Tubocurarine at low concentrations (1-5 ?m) inhibited the 5-HT induced inward current competitively. The mode of its inhibitory action became noncompetitive at higher concentrations (10-20 ?m).
Higashi, H.; Nishi, S.
[ 3H]Sumatriptan binding sites in human brain: regional-dependent labelling of 5HT 1D and 5HT 1F receptors
The general properties of [3H]sumatriptan binding sites in postmortem human brain tissue sections are described. High concentrations of autoradiographic grains were seen in globus pallidus = substantia nigra > cortex > putamen > hippocampus. While 5-HT (5-hydroxytryptamine) displaced in all regions more than 90% of [3H]sumatriptan binding, the level of binding inhibited by 5-CT (5-carboxamidotryptamine) varied in each region. Although
Julio Pascual; Carmen Del Arco; Tamara Rom¾n; Elena Del Olmo; Angel Pazos
Effect of selective 5HT 3 antagonist (GR 38032F) on small intestinal transit and release of gastrointestinal peptides
Antagonists of 5-hydroxytryptamine type 3 (5HT3) receptors reduce the nausea induced by cisplatinum, but the effects of these agents on 5HT3 receptors in the human gut remain to be defined. We examined the actions of one of these drugs (Glaxo GR 38032F) on small intestinal transit and mouth-to-cecum transit times in healthy man. We also quantified its effects on the
N. J. Talley; S. F. Phillips; A. Haddad; L. J. Miller; C. Twomey; A. R. Zinsmeister; A. Ciociola
An mRNA expression analysis of stimulation and blockade of 5HT 7 receptors during memory consolidation
Despite the compelling support for 5-hydroxytryptamine (5-HT) receptors participation in learning and memory in mammal species, the molecular basis had been largely absent from any discussion of its mechanistic underpinnings. Here, we report that reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed that there was a higher level of expression of the investigated 5-HT receptor mRNAs in autoshaping-trained relative to untrained
Georgina Pķrez-GarcĒa; Claudia Gonzalez-Espinosa; Alfredo Meneses
Role of the 5HT7 Receptor in the Central Nervous System: from Current Status to Future Perspectives
Pharmacological and genetic tools targeting the 5-hydroxytryptamine (5-HT)7 receptor in preclinical animal models have implicated\\u000a this receptor in diverse (patho)physiological processes of the central nervous system (CNS). Some data obtained with 5-HT7\\u000a receptor knockout mice, selective antagonists, and, to a lesser extent, agonists, however, are quite contradictory. In this\\u000a review, we not only discuss in detail the role of the
Anne Matthys; Guy Haegeman; Kathleen Van Craenenbroeck; Peter Vanhoenacker
Increased hypothalamic 5-HT2A receptor gene expression and effects of pharmacologic 5-HT2A receptor inactivation in obese A{sup y} mice
Serotonin (5-hydroxytryptamine; 5-HT) 2A receptors contribute to the effects of 5-HT on platelet aggregation and vascular smooth muscle cell proliferation, and are reportedly involved in decreases in plasma levels of adiponectin, an adipokine, in diabetic subjects. Here, we report that systemic administration of sarpogrelate, a 5-HT2A receptor antagonist, suppressed appetite and increased hypothalamic pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript, corticotropin releasing hormone, 5-HT2C, and 5-HT1B receptor gene expression. A{sup y} mice, which have ectopic expression of the agouti protein, significantly increased hypothalamic 5-HT2A receptor gene expression in association with obesity compared with wild-type mice matched for age. Systemic administration of sarpogrelate suppressed overfeeding, body weight gain, and hyperglycemia in obese A{sup y} mice, whereas it did not increase plasma adiponectin levels. These results suggest that obesity increases hypothalamic 5-HT2A receptor gene expression, and pharmacologic inactivation of 5-HT2A receptors inhibits overfeeding and obesity in A{sup y} mice, but did not increase plasma adiponectin levels.
Nonogaki, Katsunori [Center of Excellence, Division of Molecular Metabolism and Diabetes, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575 (Japan)]. E-mail: firstname.lastname@example.com; Nozue, Kana [Center of Excellence, Division of Molecular Metabolism and Diabetes, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575 (Japan); Oka, Yoshitomo [Center of Excellence, Division of Molecular Metabolism and Diabetes, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575 (Japan)
Induction of delayed-type hypersensitivity responses to PPD: dendritic cells in synergy with 5-hydroxytryptamine can substitute for macrophages.
We describe the use of 5-hydroxytryptamine (5HT) as an adjuvant in the induction of the delayed-type hypersensitivity (DTH) response to purified protein derivative (PPD). Based upon our previous studies with antigen-pulsed macrophages (M phi), we have shown that both the Day 2 early (2 hr) reaction and the Day 3 (24 hr) reaction are augmented if 5HT is incorporated into the priming injection. Furthermore, we have confirmed that in contrast to M phi, antigen-pulsed dendritic cells (DC) fail to prime the early (2 hr) component of DTH. However, DC do prime the early response if injected along with 5HT. A peripheral 5HT antagonist, ICS 205-930, inhibits both the M phi-mediated and the 5HT/DC-primed reactions. These findings support the hypothesis that DTH reactions require a cascade of both inflammatory and immunological signals, and that in mice vascular permeability mediated via 5HT is important in the early phase of the reaction.
Roberts, D; Katz, D R; Mukherjee, S; Rook, G A
Dissipation mechanisms for 5-hydroxytryptamine in the coronary circulation of the isolated perfused heart of the rat.
1. The contribution of uptake into vascular endothelial cells, of neuronal uptake and of extraneuronal uptake in the dissipation of 5-hydroxytryptamine (5-HT) perfused through the coronary circulation of the rat heart was examined. 2. Hearts from reserpine-pretreated rats were isolated and perfused in vitro with 5-HT, in the absence or presence of inhibitors, and rates of appearance of the deaminated metabolite, 5-hydroxyindoleacetic acid (5-HIAA), in the venous effluent were measured using an h.p.l.c. assay. 3. The steady-state rates of 5-HIAA appearance in the venous effluent in hearts perfused with 1 microM 5-HT (422 +/- 8.48 pmol g-1 min-1, n = 12) were reduced by pretreatment of the rats with 6-hydroxydopamine (22% inhibition), and by inclusion in the perfusion solution of 30 microM cocaine (28% inhibition), 100 microM 3-O-methylisoprenaline (64% inhibition), 100 microM corticosterone (58% inhibition), or 30 microM cocaine and 100 microM 3-O-methylisoprenaline (87% inhibition). 4. The extraneuronal deamination of 5-HT in the heart was saturable (Km = 101 microM, Vmax = 31.2 nmol g-1 min-1). The neuronal deamination of 5-HT was saturated by about 50 fold lower concentrations of 5-HT than was extraneuronal deamination, but Km and Vmax values could not be determined. 5. In the coronary circulation of the rat heart, 5-HT was dissipated by the uptake processes for catecholamines, extraneuronal uptake (predominantly) and neuronal uptake, and subsequent metabolism by monoamine oxidase. There was no evidence that a cocaine-sensitive uptake of 5-HT into vascular endothelial cells made any significant contribution to 5-HT dissipation in the heart.
Bryan, L. J.; O'Donnell, S. R.; Williams, A. M.
Assessment of 5-hydroxytryptamine efflux in rat brain during a mild, moderate and severe serotonin-toxicity syndrome
Serotonin (5-hydroxytryptamine; 5-HT)-toxicity syndrome, an iatrogenic brain disorder induced by excessive efflux of 5-HT, has received much attention because of increasing incidents of serotonergic antidepressants. However, the neural mechanism by which extracellular 5-HT is elevated to a toxic level for the syndrome remains to be determined. The goal of the present study was to test the hypothesis that extracellular 5-HT is composed of two component effluxes responsible for distinct aspects of the syndrome. The first set of experiments was to characterize the syndrome by measuring changes in neuromuscular signs, body-core temperature and mortality rate. Our results indicate that the syndrome severity can be categorized into mild, moderate and severe levels. The second set of experiments was to determine a threshold of extracellular 5-HT for induction of each level of the syndrome. Our results demonstrate that there were an 11-fold increase in the mild syndrome and an over 55-fold increase in the severe syndrome. In the last series of experiments, the excessive increases in 5-HT were pharmacologically separated into primary and secondary component effluxes with the 5-HT2A receptor antagonists cyproheptadine and ketanserin and NMDA receptor antagonist (+)-MK-801. Our results suggest primary component efflux was caused by direct drug effects on 5-HT biosynthetic and metabolic pathways and secondary efflux ascribed to indirect drug effect on a positive feedback circuit involving 5-HT2A and NMDA receptors. In summary, the primary efflux could be an initial cause for the induction of the syndrome while the secondary efflux might involve deterioration of the syndrome.
Zhang, Gongliang; Krishnamoorthy, Swapna; Ma, Zhiyuan; Vukovich, Nick P.; Huang, Xupei; Tao, Rui
Molecular cloning and pharmacological characterization of serotonin 5-HT(3A) receptor subtype in dog.
In order to establish if the canine 5-hydroxytryptamine type 3A (5-HT(3A)) receptors share the pharmacological profile with human 5-HT(3A) receptors, we cloned and performed a molecular pharmacological characterization of the canine 5-HT(3A) receptor. The 5-HT(3A) cDNA was cloned from canine brain by polymerase chain reaction amplification. It encodes a 483 amino acid peptide that exhibits from 80% (mice) to 90% (ferrets) identity to other sequenced mammalian 5-HT(3A) receptors. The receptor agonists 5-hydroxytryptamine (5-HT) and meta-chlorophenylbiguanide (mCPBG) showed little differences between the two species, whereas 2-methyl-5-hydroxytryptamine (2-Me-5-HT) was ten times weaker at canine receptors than at human receptors. The potencies at the canine 5-HT(3) receptors were 9.9 microM (5-HT), 79 microM (2-Me-5-HT) and 0.8 microM (mCPBG). The selective, competitive receptor antagonist ondansetron was ten times more potent at human receptors compared to canine receptors (K(b)=0.9 nM), while (+)-tubocurarine was 1000-fold more potent at canine receptors (K(b)=3.0 nM) than at human receptors. Examination of the presumed ligand binding extracellular domain revealed one residue, where the canine receptor differs from all previously characterized 5-HT(3A) receptors, i.e. other species contain a conserved Trp(195), whereas the canine orthologue contains a Leu(195). To address the differences in potencies at the human and canine 5-HT(3A) receptors seen in this study, we introduced a L195W point mutation in the canine orthologue. Data showed that the 195 residue can affect receptor agonist potency and efficacy as well as antagonist potency, but did produce a pharmacological profile identical to the human orthologue. We therefore conclude that position 195 is strongly involved in the receptor-ligand interaction, but additional residues must contribute to the overall pharmacological profile. PMID:16647053
Jensen, Thomas N; Nielsen, Jacob; Frederiksen, Kristen; Ebert, Bjarke
RNA editing induces variation in desensitization and trafficking of 5-hydroxytryptamine 2c receptor isoforms.
The 5-hydroxytryptamine2c receptor (5-HT2cR) is subjected to RNA editing, in the second intracellular loop, generating 14 different isoforms in human brain. This post-transcriptional event markedly alters the signaling properties of the receptor by reducing its ability to couple to G-proteins. Although the non-edited form of the receptor is essentially fully constitutively active, edited forms show lesser degrees of constitutive activity. We have used two extensively edited receptor isoforms, VGV and VSV, and the non-edited INI isoform to investigate how variations in constitutive receptor activity affect the trafficking and the interaction of these isoforms with components of the desensitization machinery in HEK 293 cells. We found that cell surface expression of the 5-HT2cR decreased in parallel with increased constitutive activity of the isoforms. The subcellular distribution of the various isoforms was dependent of their ability to interact with betaarrestin2, which correlated with the constitutive activity level of each isoform. We observed that the agonist-independent interaction of betaarrestin2 with constitutively active 5-HT2cR isoforms was reversed by inverse agonist treatments promoting receptor redistribution to the cell surface. Overexpression of a G-protein-coupled receptor kinase (GRK2) was able to stabilize the interaction of betaarrestin2 with constitutively active 5-HT2cR isoforms even in the presence of inverse agonists. Taken together, our observations indicate that the constitutively active 5-HT2cR isoforms are spontaneously internalized in an agonist-independent manner. This endocytosis process is mediated by a GRK/betaarrestin-dependent mechanism and is directly correlated with the constitutive activity status of the RNA edited receptor variants. Thus the ultimate physiological output of constitutively active receptors may be determined not only by their agonist-independent activity but also by their interactions with GRKs and betaarrestin. PMID:14602721
Marion, Sķbastien; Weiner, David M; Caron, Marc G
Characterization of the binding of 3H-norzimeldine, a 5-HT uptake inhibitor, to rat brain homogenates.
The binding of radiolabelled norzimeldine, a potent selective 5-HT reuptake inhibitor, to rat brain homogenates is described. 3H-Norzimeldine binds to a site with high affinity (KD = 10.5 nM) in a saturable manner (Bmax = 15.4 pmol/g wet weight in the cerebral cortex). The number of binding sites in the various regions of the brain parallels the capacity of the 5-HT reuptake mechanism. Drugs that inhibit the reuptake of 5-HT are also potent inhibitors of the 3H-norzimeldine binding, as are the tricyclic antidepressants, which are non-specific inhibitors of the noradrenaline and the 5-HT reuptake. Lesioning experiments using DSP4 (a NA neurotoxin) and p-chloroamphetamine (a 5-HT neurotoxin) suggest that the binding site is located on the presynaptic 5-HT nerve terminal, although a small component of the binding may be to noradrenergic uptake sites as well. PMID:6235721
Hall, H
Ion permeation through 5-hydroxytryptamine-gated channels in neuroblastoma N18 cells
Ionic currents induced by 5-hydroxytryptamine (5-HT) in cultured neuroblastoma N18 cells were studied using whole-cell voltage clamp. The response was blocked by 1-10 nM 5-HT3 receptor-specific antagonists MDL 7222 or ICS 205-930, but not by 1 microM 5-HT1/5-HT2 receptor antagonist spiperone or 5-HT2 receptor-specific antagonist ketanserin. These 5-HT3 receptors seem to be ligand-gated channels because the response (a) did not require internal ATP or GTP, (b) persisted with long internal dialysis of CsF (90 mM), A1F4- (100 microM), or GTP gamma S (100 microM), and (c) with ionophoretic delivery of 5-HT developed with a delay of less than 10 ms and rose to a peak in 34-130 ms. Fluctuation analysis yielded an apparent single-channel conductance of 593 fS. The relative permeabilities of the channel for a variety of ions were determined from reversal potentials. The channel was only weakly selective among small cations, with permeability ratios PX/PNa of 1.22, 1.10, 1.01, 1.00, and 0.99 for Cs+, K+, Li+, Na+, and Rb+, and 1.12, 0.79, and 0.73 for Ca2+, Ba2+, and Mg2+ (when studied in mixtures of 20 mM divalent ions and 120 mM N-methyl-D-glucamine). Apparent permeability ratios for the divalent ions decreased as the concentration of divalent ions was increased. Small monovalent organic cations were highly permeant. Large organic cations such as Tris and glucosamine were measurably permeant with permeability ratios of 0.20 and 0.08, and N-methyl-D-glucamine was almost impermeant. Small anions, NO3-, Cl-, and F-, were slightly permeant with permeability ratios of 0.08, 0.04, and 0.03. The results indicate that the open 5-HT3 receptor channel has an effective minimum circular pore size of 7.6 A and that ionic interactions in the channel may involve negative charges near the pore mouth.
Pharmacological analysis of the interaction between Bay K 8644 and 5-HT in rabbit aorta.
Bay K 8644 potentiated and augmented 5-hydroxytryptamine (5-HT)-induced contractions in the rabbit, isolated aorta preparation, as manifested in leftward shift and increase in the asymptote of 5-HT E/[A] (effect vs concentration) curves. The operational model of agonism (Black & Leff, 1983) was used to analyse this interaction and the concomitant effects of irreversible receptor alkylation by phenoxybenzamine. The competitive effects of spiperone in the presence and absence of Bay K 8644 were also examined. From these analyses it is concluded that Bay K 8644 elicits its potentiating effects by increasing the efficacy of 5-HT at the 5-HT2 receptor with no alteration in affinity. This is consistent with the known effect of Bay K 8644 of causing an increase in the functional concentration of plasmalemmal calcium channels coupled to the 5-HT2 receptors in this preparation. The positively co-operative shape of the 5-HT E/[A] curves obtained in the aorta and the quantitative nature of their potentiation by Bay K 8644 indicated that the coupling of 5-HT2 receptor occupancy to intracellular calcium concentration is linear and that the co-operativity resides in the subsequent relation between intracellular calcium and pharmacological effect. Bay K 8644 may serve as a probe for differentiating between the types of calcium channels that transduce 5-HT receptor-mediated effects in different systems. Such information would be useful in the classification of agonist interactions with 5-HT receptors.
Barrett, V. J.; Leff, P.; Martin, G. R.; Richardson, P. J.
The anti-emetic potential of the 5-hydroxytryptamine3 receptor antagonist BRL 43694.
In ferrets, the selective 5-hydroxytryptamine (5-HT) 5-HT3 receptor antagonist BRL 43694 given as a single injection (0.05-0.5 mg kg-1 i.v.) before cisplatin, or by divided dose (2 x 0.005-2 x 0.5 mg kg-1 i.v.) before and after cisplatin dramatically reduced or abolished the severe cisplatin-induced vomiting. BRL 43694 also substantially reduced the vomiting induced by cyclophosphamide:doxorubicin, and prevented the trimelamol-induced emesis. The severe emesis caused by whole body exposure to X-irradiation was prevented by intravenous or oral BRL 43694. A single i.v. dose of BRL 43694 given during an emetic episode or within the peak emetic period, abolished the vomiting induced by the cytotoxic drugs and by X-irradiation, usually within 30 s. Where the induction of emesis was prevented or subsequently abolished by BRL 43694, the associated behaviour (subjectively assessed as nausea) was also absent or greatly attenuated. BRL 43694 (0.1 mg kg-1 i.v.) did not affect the emesis evoked in dogs by the dopamine agonist apomorphine. The potent anti-emetic activity of BRL 43694 is discussed in terms of potential clinical use, and of the fundamental role that 5-HT3 receptors may play in the mechanisms of nausea and vomiting.
Bermudez, J.; Boyle, E. A.; Miner, W. D.; Sanger, G. J.
5-Hydroxytryptamine release from platelets by different red wines: implications for migraine.
We have confirmed our earlier finding that most red wines are able to bring about 5-hydroxytryptamine (5-HT, serotonin) release from platelets in vitro. Platelets from individual subjects manifested varying degrees of releasing ability but responded to different wines with a similar rank ordering. There was a high correlation (r = 0.87) between the effect of red wine and that of reserpine in different individuals. Some types of red wine caused a consistently higher release of 5-HT than others in all subjects; one red wine in particular resulted in negligible release. When several brands of this 'low-releasing' red wine were further examined, they all showed a lower activity than all the brands of a 'high-releasing' red wine type. This variation in releasing power was not related to intensity of red colour. Partial purification of red wine was achieved by column chromatography and showed releasing activity to be associated with a low molecular weight orange fraction. Preliminary studies, using solid phase extraction methods, showed that the active components lie mainly in a subgroup of the flavonoid fraction. If any of the adverse effects of red wine, such as headache induction, derive from this 5-HT releasing ability, then it may be possible to prepare red wines free from the chemical substances responsible. PMID:7720790
Pattichis, K; Louca, L L; Jarman, J; Sandler, M; Glover, V
5-HT potentiation of the GABA(A) response in the rat sacral dorsal commissural neurones.
1. The modulatory effect of 5-hydroxytryptamine (5-HT) on the gamma-aminobutyric acid(A) (GABA(A)) response was investigated in the neurones freshly dissociated from the rat sacral dorsal commissural nucleus (SDCN) using the nystatin perforated patch recording configuration under the voltage-clamp conditions. 2. 5-HT potentiated GABA-induced Cl- current (IGABA) without affecting the reversal potential of IGABA and the apparent affinity of GABA to its receptor. 3. Alpha-Methyl-5-HT mimicked the potentiation effect of 5-HT on IGABA while ketanserine blocked it. 1-Oleoyl-2-acetyl-glycerol (OAG) potentiated IGABA, and the effect of 5-HT on IGABA was occluded by OAG pretreatment. In the presence of chelerythrine, 5-HT failed to potentiate IGABA, suggesting that protein kinase C (PKC) is involved in the pathway through which the activation of the 5-HT2 receptor potentiates the IGABA. 4. The facilitatory effect of 5-HT on IGABA remained in the presence of BAPTA-AM. LiCl also had no effect on 5-HT-induced potentiation of IGABA. 5. H-89, genistein, okadaic acid and pervanadate all had no effects on 5-HT potentiation of IGABA. Pertussis toxin treatment for 6-8 h did not block the facilitatory effect of 5-HT on IGABA. 6. The present results show that GABA(A) receptor in the rat SDCN could be modulated in situ by 5-HT, one of the major transmitters involved in the supraspinal control of nociception, and that the phosphorylation of GABA(A) receptor by PKC may be sufficient to support such modulation. The results also strongly support the hypothesis that the cotransmission by 5-HT and GABA has an important role in the spinal cord. PMID:9690871
Xu, T L; Pang, Z P; Li, J S; Akaike, N
5-HT potentiation of the GABAA response in the rat sacral dorsal commissural neurones
The modulatory effect of 5-hydroxytryptamine (5-HT) on the ?-aminobutyric acidA (GABAA) response was investigated in the neurones freshly dissociated from the rat sacral dorsal commissural nucleus (SDCN) using the nystatin perforated patch recording configuration under the voltage-clamp conditions.5-HT potentiated GABA-induced Cl? current (IGABA) without affecting the reversal potential of IGABA and the apparent affinity of GABA to its receptor.?-Methyl-5-HT mimicked the potentiation effect of 5-HT on IGABA while ketanserine blocked it. 1-Oleoyl-2-acetyl-glycerol (OAG) potentiated IGABA, and the effect of 5-HT on IGABA was occluded by OAG pretreatment. In the presence of chelerythrine, 5-HT failed to potentiate IGABA, suggesting that protein kinase C (PKC) is involved in the pathway through which the activation of the 5-HT2 receptor potentiates the IGABA.The facilitatory effect of 5-HT on IGABA remained in the presence of BAPTA-AM. LiCl also had no effect on 5-HT-induced potentiation of IGABA.H-89, genistein, okadaic acid and pervanadate all had no effects on 5-HT potentiation of IGABA. Pertussis toxin treatment for 6¢8?h did not block the facilitatory effect of 5-HT on IGABA.The present results show that GABAA receptor in the rat SDCN could be modulated in situ by 5-HT, one of the major transmitters involved in the supraspinal control of nociception, and that the phosphorylation of GABAA receptor by PKC may be sufficient to support such modulation. The results also strongly support the hypothesis that the cotransmission by 5-HT and GABA has an important role in the spinal cord.
Xu, Tian-Le; Pang, Zhi-Ping; Li, Ji-Shuo; Akaike, Norio
5-HT2 Receptors Facilitate JC Polyomavirus Entry
The human JC polyomavirus (JCPyV) causes the rapidly progressing demyelinating disease progressive multifocal leukoencephalopathy (PML). The disease occurs most often in individuals with AIDS but also occurs in individuals receiving immunomodulatory therapies for immune-related diseases such as multiple sclerosis. JCPyV infection of host cells requires the pentasaccharide lactoseries tetrasaccharide c (LSTc) and the serotonin receptor 5-hydroxytryptamine (5-HT) receptor 5-HT2AR. While LSTc is involved in the initial attachment of virus to cells via interactions with VP1, the mechanism by which 5-HT2AR contributes to infection is not clear. To further define the roles of serotonin receptors in infection, HEK293A cells, which are poorly permissive to JCPyV, were transfected with 14 different isoforms of serotonin receptor. Only 5-HT2 receptors were found to support infection by JCPyV. None of the other 11 isoforms of serotonin receptor supported JCPyV infection. Expression of 5-HT2 receptors did not increase binding of JCPyV to cells, but this was not unexpected, given that the cells uniformly expressed the major attachment receptor, LSTc. Infection of these cells remained sensitive to inhibition with soluble LSTc, confirming that LSTc recognition is required for JCPyV infection. Virus internalization into HEK293A cells was significantly and specifically enhanced when 5HT2 receptors were expressed. Taken together, these data confirm that the carbohydrate LSTc is the attachment receptor for JCPyV and that the type 2 serotonin receptors contribute to JCPyV infection by facilitating entry.
Assetta, Benedetta; Maginnis, Melissa S.; Gracia Ahufinger, Irene; Haley, Sheila A.; Gee, Gretchen V.; Nelson, Christian D. S.; O'Hara, Bethany A.; Allen Ramdial, Stacy-ann A.
Alprazolam potentiates the antiaversive effect induced by the activation of 5HT 1A and 5HT 2A receptors in the rat dorsal periaqueductal gray
RationaleĀĀSerotonin in the dorsal periaqueductal gray (DPAG) through the activation of 5-HT1A and 5-HT2A receptors inhibits escape, a defensive behavior associated with panic attacks. Long-term treatment with antipanic drugs that\\u000a nonselectively or selectively blocks the reuptake of serotonin (e.g., imipramine and fluoxetine, respectively) enhances the\\u000a inhibitory effect on escape caused by intra-DPAG injection of 5-HT1A and 5-HT2A receptor agonists. It
ValquĒria Camin de Bortoli; Regina L·cia Nogueira; Hķlio Zangrossi Jr
Age-related changes in the effects of 5-hydroxytryptamine on substantia gelatinosa neurons of the trigeminal subnucleus caudalis.
The trigeminal subnucleus caudalis (Vc) is the critical brainstem relay site of orofacial nociceptive processing to higher brain centers. The descending serotonergic pathway from the brainstem exerts inhibitory or facilitatory effects on nociceptive transmission in the spinal dorsal horn and the Vc, and SG neurons of the Vc exhibit hyperpolarization, no response or depolarization in response to 5-hydroxytryptamine (5-HT) application. In this study, we examined age-related changes in the effects of 5-HT on SG neurons of the Vc using immature, peripubertal and adult male mice and gramicidin-perforated patch recordings under the current-clamp mode. In the three age groups, hyperpolarization was the major response in SG neurons exhibiting membrane potential changes in response to 5-HT application. The proportion of the SG neurons responding to 5-HT by hyperpolarization was significantly higher in the immature (20/27) than in the adult mice (10/26; P<0.05). The proportion of SG neurons showing no response to 5-HT was significantly higher in the peripubertal (11/21) and the adult mice (13/26) compared with the immature mice (5/27). The amplitude of 5-HT-induced hyperpolarization significantly decreased with increasing postnatal age (correlation coefficient=-0.43, P<0.05). The mean amplitude of 5-HT-induced hyperpolarization was significantly higher in the immature mice (-9.7▒1.1 mV, n=20) than in the peripubertal (-5.3▒1.0 mV, n=10) and the adult mice (-5.4▒0.9 mV, n=10; both P<0.05). These results suggest that the descending serotonergic modulatory influence over the orofacial nociceptive processing in the Vc may change during postnatal development and postnatal age of three weeks is a critical period for changes in 5-HT-induced hyperpolarizing effects in mice. PMID:22260792
Park, Seon Ah; Yang, Eun Ju; Han, Seong Kyu; Park, Soo Joung
Membrane potential changes induced by 5-hydroxytryptamine in the rabbit superior cervical ganglion.
1. Changes in resting membrane potential induced by 5-hydroxytryptamine (5-HT) have been measured in the excised ganglion by the sucrose-gap technique. 2. 5-HT produced a rapid depolarization, the threshold concentration for depolarization being around 10 muM. With concentrations of 100 muM or greater, repolarization began during the course of the superfusion; this was followed by prolonged tachyphylaxis. 3. Tachyphylaxis was largely avoided by making injections into the superfusion stream. Standard injections of 0.2 mumol 5-HT dissolved in 0.2 ml of Krebs solution were used routinely and could be given at 20-30 min intervals to evoke relatively constant responses. 4. The response to an injection consisted of a rapid depolarization, followed by a rapid repolarization and subsequent after-hyperpolarization. The threshold quantity for depolarization was around 0.01 mumol, while the ED50 estimated from 6 dose-response curves was 0.12 +/- 0.02 mumol (mean +/- s.e. mean). 5. Injections of 5-HT (0.2 mumol), choline (10 mumol) and acetylcholine (9.9 mumol) produced depolarizations of similar magnitude. 6. Monoamine oxidase inhibitors failed to alter substantially the amplitude of depolarizations to 5-HT. 7. 5-HT depolarizations were unaltered in amplitude when the impermeant anion benzenesulphonate was substituted for the chloride ion in Krebs solution, but were initially markedly reduced in amplitude in a sodium-deficient medium; some recovery of the response subsequently occurred. The depolarization which persisted in sodium-deficient solutions was much reduced or abolished when calcium ions were then removed from the superfusion medium. Removal of either calcium ions alone or potassium ions from the superfusion fluid did not reduce depolarization amplitude. 8. The after-hyperpolarization was abolished in sodium-deficient solutions, usually increased in potassium-free solutions, reduced or abolished by ouabain or nicotine, but unaffected by calcium free solutions. 9. A depolarizing action of 5-HT on presynaptic terminals in the ganglion appears probable.
Wallis, D I; Woodward, B
Subunit rotation models activation of serotonin 5HT 3AB receptors by agonists
Summary The N-terminal extracellular regions of heterooligomeric 3AB-type human 5-hydroxytryptamine receptors (5-HT 3ABR) were modelled based on the crystal structure of snail acetylcholine binding protein AChBP. Stepwise rotation of subunit A by 5░ was performed between -10░ and 15░ to mimic agonist binding and receptor activation. Anticlockwise rotation reduced the size of the binding cavity in interface AB and reorganised
Gßbor Maksay; Mikl¾s Simonyi; Zsolt Bikßdi
Increased defaecation caused by 5HT 4 receptor activation in the mouse
The precursor to 5-hydroxytryptamine (5-HT), 5-hydroxytryptophan, (5-HTP, 5¢50 mg Ę kg?1) administered subcutaneously (s.c.) to conscious, fed mice caused a dose dependent increase in faecal pellet and fluid output. To avoid provoking watery diarrhoea, all experiments were performed using 5-HTP at 10 mg Ę kg?1. This dose caused maximal increases in the fluid content (471 ▒ 41%) and number of
Stephen E. Banner; Martin I. Smith; Darren Bywater; Laramie M. Gaster; Gareth J. Sanger
5-HT2A SEROTONIN RECEPTOR BIOLOGY: Interacting proteins, kinases and paradoxical regulation
5-hydroxytryptamine2A (5-HT2A) serotonin receptors are important pharmacological targets for a large number of central nervous system and peripheral serotonergic medications. In this review article I summarize work mainly from my lab regarding serotonin receptor anatomy, pharmacology, signaling and regulation. I highlight the role of serotonin receptor interacting proteins and the emerging paradigm of G-protein coupled receptor functional selectivity.
Roth, Bryan L
Increased gastric motility during 5-HT4 agonist therapy reduces response fluctuations in Parkinson's disease.
We investigated the clinical efficacy and tolerability of 45 mg/day mosapride, a selective 5-hydroxytryptamine type 4 (5-HT4) agonist, in an open-label study involving five patients with Parkinson's disease (PD) who had response fluctuations (RFs). 'On' time and motor function scores were determined, and gastric motility was measured by a radionuclide gastric emptying (GE) test, the most reliable quantitative method available. We found that mosapride therapy significantly shortened GE half-time, reduced RFs, and improved motor functions in all patients. There were no adverse reactions. We conclude that selective 5-HT4 agonist therapy is beneficial for patients with PD who have RFs. PMID:16263322
Asai, Hirohide; Udaka, Fukashi; Hirano, Makito; Minami, Takeshi; Oda, Masaya; Kubori, Tamotsu; Nishinaka, Kazuto; Kameyama, Masakuni; Ueno, Satoshi
Serotonin 5HT 7 receptors coupled to induction of interleukin-6 in human microglial MC3 cells
Brain serotonin 5-HT7 receptors are known to be expressed in neurons and astrocytes. We now report the presence of these receptors in a third type of cell, microglial cells. 5-Hydroxytryptamine (5-HT), 5-carboxamidotryptamine (5-CT), 5-methoxytryptamine (5-MeOT) and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) induced concentration-dependent stimulations of cAMP accumulation in the human microglial MC-3 cell line. The maximal effect of 5-HT was 3.4▒0.3-fold stimulation (mean▒S.E.M.,
Cķcile Mahķ; Erika Loetscher; Kumlesh K. Dev; Ionel Bobirnac; Uwe Otten; Philippe Schoeffter
In vivo assessment of acceleration of motor activity associated with acetylcholine release via 5-hydroxytryptamine4 receptor in dog intestine.
Effect of mosapride, a benzamide, on the motor activity associated with the release of endogenous acetylcholine (ACh) from enteric neurons was examined in the ileum of anesthetized dogs using an in vivo microdialysis method and compared with the effect of 5-hydroxytryptamine (5-HT). Intraarterial administration of 5-HT accelerated intestinal motor activity and increased the concentration of dialysate ACh, and the responses were inhibited by SB204070, a specific 5-HT4-receptor antagonist, but were apparently not affected by methiothepin, ketanserin and granisetron. Intraarterial administration of mosapride, a prokinetic benzamide, accelerated intestinal motor activity and the concentration of dialysate ACh increased. The effects of mosapride were antagonized by SB204070. Specific [125I]SB207710 binding was observed in the myenteric and submucosal plexuses and muscle layers of dog ileum by in vitro receptor autoradiography. High densities of [125I]SB207710 binding sites were detected in the myenteric and submucosal plexuses. Mosapride as well as SB204070 inhibited [125I]SB207710 binding. Thus, in the whole body of dogs, 5-HT and mosapride accelerated the intestinal motor activity due to the increases in ACh release mediated by stimulation of the 5-HT4 receptor. PMID:12396025
Makimoto, Noriaki; Sakurai-Yamashita, Yasuko; Furuichi, Akira; Kawakami, Shunsuke; Enjoji, Akihito; Kanematsu, Takashi; Taniyam, Kohtaro
6-Substituted tricyclic partial ergoline compounds are selective and potent 5-hydroxytryptamine sub 1A receptor agents
A series of 6 tricyclic partial ergoline derivatives was analyzed using radioligand binding assays. Four agents (LY 178210, LY 254089, LY 197205, and LY 197206) display high affinity for 5-hydroxytryptamine{sub 1A} (5-HT{sub 1A}) receptor binding sites labeled by ({sup 3}H)8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) and display {ge} 150 fold selectivity for the 5-HT{sub 1A} over the 5-HT{sub 1D} receptor binding site. The most potent agent investigated, LY 178210, is essentially inactive at a total of 12 other neurotransmitter receptor binding sites in the brain. Using a forskolin-stimulated adenylate cyclase assay as a model of 5-HT{sub 1A} receptor function, LY 178210 was found to display partial agonist activity which was blocked by 10{sup {minus}5} M ({minus})pindolol. These data indicate that LY 178210 is a potent and selective 5-HT{sub 1A} receptor partial agonist.
Slaughter, J.L.; Harrington, M.A.; Peroutka, S.J. (Stanford Univ. School of Medicine, CA (USA))
Subchronic fluoxetine administration to rats: effects on 5-HT autoreceptor activity as measured by in vivo microdialysis.
Subchronic administration of fluoxetine to rats has been shown to induce subsensitivity of presynaptic 5-HT(1A) and 5-HT(1B) autoreceptors, and also postsynaptic 5-HT(1A) receptors in the hypothalamus. We investigated the effects of administration of fluoxetine (10 mg/kg i.p.) to rats for 6 days on presynaptic 5-HT(1A) receptor activity in the hypothalamus, postsynaptic 5-HT(1A) receptor activity in the hippocampus, and presynaptic 5-HT(1B) autoreceptor activity in both areas, using in vivo microdialysis. The effect of the 5-HT(1B/1D) antagonist (N-[4-methoxy-3-(4-methyl-1-piperizinyl)phenyl]-2'-methyl-4'-(5- methyl-1,2,4-oxadiazole-3-yl)[1,1'-biphenyl]-carboxamide (GR 127935) (5 mg/kg s.c.) to elevate 5-hydroxytryptamine (5-HT) levels was reduced in hippocampus but not hypothalamus of fluoxetine-treated rats. Fluoxetine did not alter either presynaptic 5-HT(1A) autoreceptor activity, as measured by the effect of injection of 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT) (0.2 mg/kg or 50 microg/kg s.c.) on 5-HT levels in the hypothalamus, or postsynaptic 5-HT(1A) receptor activity, as measured by the effect of 8-OH-DPAT (0.2 mg/kg s.c.) on cyclic AMP accumulation, in the hippocampus. PMID:10871704
Dremencov, E; Gur, E; Lerer, B; Newman, M E
Expression of 5-HT3 receptors in PC12 cells treated with NGF and 8-Br-cAMP.
1. To determine the functional development of neurons, we applied nerve growth factor (NGF) or 8-bromo-cyclic-adenosine monophosphate (8-Br-cAMP) to PC12 cells and recorded the 5-hydroxytryptamine (5-HT)-induced response by the use of a patch-clamp technique. 2. Cultured PC12 cells expressed 5-HT-sensitive receptors, which are almost absent in untreated cells, in the continuous presence of NGF or 8-Br-cAMP for a period of 10 days. 3. Activation of the receptors by 5-HT produced a transient inward current. In a K(+)-free solution, the reversal potential (E5-HT) of I5-HT was +10.3 mV, and the current-voltage (I-V) relation showed inward rectification at positive potentials. 4. The permeability ratio for monovalent cations was Na+:Li+:K+:Rb+:Cs+ = 1:1.19:0.89:0.94:0.91, indicating that a 5-HT-induced current is passing through the ligand-gated large cation channel. 5. 2-Methyl-5-HT, a specific 5-HT3 agonist, induced a similar inward current, even though the current amplitude was smaller and the activation and inactivation kinetics were slower than those of 5-HT. 6. ICS-205-930, a specific 5-HT3 antagonist, inhibited the 5-HT-induced current in a concentration-dependent manner with a noncompetitive inhibition profile. Spiperone, a 5-HT1 and 5-HT2 families antagonist, and ketanserine, 5-HT2 family antagonist, did not affect the 5-HT-induced response. 7. The time to peak (tp) as well as fast and slow time constants (tau if and tau is) decreased with increasing 5-HT concentration.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1588384
Furukawa, K; Akaike, N; Onodera, H; Kogure, K
Control of 5-hydroxytryptamine release in the dorsal raphe nucleus by the noradrenergic system in rat brain. Role of alpha-adrenoceptors.
The interactions between the brainstem serotonergic (5-hydroxytryptamine, 5-HT) and noradrenergic (NA) systems are important for the pathophysiology and treatment of affective disorders. We examined the influence of alpha-adrenoceptors on 5-HT and NA release in the rat dorsal raphe nucleus (DR) using microdialysis. 5-HT and NA concentrations in DR dialysates were virtually suppressed by TTX and increased by veratridine. The local and systemic administration of the alpha(1)-adrenoceptor antagonist prazosin reduced the DR 5-HT output but not that of NA. The maximal 5-HT reduction induced by local prazosin administration (-78% at 100 microM) was more marked than by its systemic administration (-43% at 0.3 mg/kg). The local application of NA and desipramine, to increase the tone on DR alpha(1)-adrenoceptors, did not enhance 5-HT release. The local (100 microM) or systemic (0.1-1 mg/kg s.c.) administration of clonidine reduced 5-HT and NA release (-48 and -79%, respectively, at 1 mg/kg), an effect reversed by RX-821002, which by itself increased both amines when given systemically. DSP-4 pretreatment prevented the effects of clonidine on 5-HT, suggesting the participation of alpha(2)-adrenoceptors on NA elements. Moreover, the systemic effect of clonidine on 5-HT (but not NA) was cancelled by lesion of the lateral habenula and by anesthesia, and was slightly enhanced by cortical transection. These data support the view that alpha(1)-adrenoceptors in the DR tonically stimulate 5-HT release, possibly at nearly maximal tone. Likewise, the 5-HT release is modulated by alpha(2)-adrenoceptors in NA neurons and in forebrain areas involved in the distal control of 5-HT neurons. PMID:12629522
Bortolozzi, A; Artigas, F
The 5-HT1A receptor and 5-HT transporter in temporal lobe epilepsy
Objective: To study 5-HT transport and 5-HT1A receptors in temporal lobe epilepsy (TLE) and depression. Methods: Thirteen patients had PET with [11C]DASB for 5-HTT and [18F]FCWAY for 5-HT1A receptor binding, MRI, and psychiatric assessment. Sixteen healthy volunteers had [11C]DASB, 19 had [18F]FCWAY, and 6 had both PET studies. We used a reference tissue model to estimate [11C]DASB binding. [18F]FCWAY volume of distribution was corrected for plasma-free fraction. Images were normalized to common space. The main outcome was the regional asymmetry index. Positive asymmetry indicates relative reduced binding (reflecting transporter activity) ipsilateral to epileptic foci. Results: Mean regional [11C]DASB binding and asymmetry did not differ between patients and controls. [18F]FCWAY asymmetry was significantly greater for patients than controls in hippocampus, amygdala, and fusiform gyrus. On analysis of variance with region as a repeated measure, depression diagnosis had a significant effect on [11C]DASB asymmetry, with significantly higher [11C]DASB asymmetry in insular cortex (trend for fusiform gyrus). In insular cortex, patients had a significant correlation between [18F]FCWAY asymmetry and [11C]DASB asymmetry. Conclusions: Our study showed increased [11C]DASB asymmetry in insula and fusiform gyrus, and relatively reduced transporter activity, in subjects with both TLE and depression, as compared to subjects with TLE alone, implying reduced reuptake and thus increased synaptic 5-HT availability. This finding may represent a compensatory mechanism for 5-HT1A receptor loss. Altered serotonergic mechanisms have an important role in TLE and concomitant depression.
Martinez, Ashley; Finegersh, Andrey; Cannon, Dara M.; Dustin, Irene; Nugent, Alison; Herscovitch, Peter
Regulation of rat cortical 5-hydroxytryptamine2A-receptor mediated electrophysiological responses by repeated daily treatment with electroconvulsive shock or imipramine
Down-regulation of 5-hydroxytryptamine2A (5-HT2A) receptors has been a consistent effect induced by most antidepressant drugs. In contrast, electroconvulsive shock (ECS) up-regulates the number of 5-HT2A receptor binding sites. However, the effects of antidepressants on 5-HT2A receptor-mediated responses on identified cells of the cerebral cortex has not been examined. The purpose of the present study was to compare the effects of the tricyclic antidepressant imipramine and ECS on 5-HT2A receptor-mediated electrophysiological responses involving glutamatergic and GABAergic neurotransmission in the rat medial prefrontal cortex (mPFC) and piriform cortex, respectively. The electrophysiological effects of activating 5-HT2A receptors was consistent with 5-HT2A receptor binding regulation for imipramine and ECS except for the mPFC where chronic ECS decreased the potency of 5-HT at a 5-HT2A receptor-mediated response. These findings are consistent with the general hypothesis that chronic antidepressant treatments shift the balance of serotonergic neurotransmission towards inhibitory effects in the cortex.
Marek, Gerard J.
Effects of chronic treatment with escitalopram or citalopram on extracellular 5-HT in the prefrontal cortex of rats: role of 5-HT1A receptors
Microdialysis was used to study the acute and chronic effects of escitalopram (S-citalopram; ESCIT) and chronic citalopram (CIT), together with the 5-HT1A receptor antagonist WAY100,635 (N-[2-[methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexane carboxamide trihydrochloride) and the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), on extracellular 5-hydroxytryptamine (5-HT) levels in the rat prefrontal cortex. Extracellular 5-HT rose to 234 and 298% of basal values after subcutaneous (s.c.) acute doses of 0.15 and 0.63 mg kg?1 ESCIT. No further increase was observed at 2.5 mg kg?1 ESCIT (290%). The effect of 13-day s.c. infusion of 10 mg kg?1day?1 ESCIT on extracellular 5-HT (422% of baseline) was greater than after 2 days (257% of baseline), whereas exposure to ESCIT was similar. In contrast, the increase in extracellular 5-HT induced by the infusion of CIT for 2 (306%) and 13 days (302%) was similar. However, brain and plasma levels of S-citalopram in rats infused with CIT for 13 days were lower than after 2 days. Acute treatment with 2.5 mg kg?1 ESCIT or 5 mg kg?1 CIT raised extracellular 5-HT by 243 and 276%, respectively, in rats given chronic vehicle but had no effect in rats given ESCIT (10 mg kg?1 day?1) or CIT (20 mg kg?1 day?1) for 2 or 13 days, suggesting that the infused doses had maximally increased extracellular 5-HT. WAY100,635 (0.1 mg kg?1 s.c.) increased extracellular 5-HT levels by 168, 174 and 169% of prechallenge values in rats infused with vehicle or ESCIT for 2 or 13 days, respectively. WAY100,635 enhanced extracellular 5-HT levels to 226, 153 and 164% of prechallenge values in rats infused with vehicle or CIT for 2 and 13 days, respectively. 8-OH-DPAT (0.025 mg kg?1) reduced extracellular 5-HT by 54% in control rats, but had no effect in those given ESCIT and CIT for 13 days. This series of experiments led to the conclusion that chronic treatment with ESCIT desensitizes the 5-HT1A receptors, regulating the release of 5-HT in the prefrontal cortex and enhances the effect of the drug on extracellular 5-HT. They also indicate that chronic treatment with ESCIT and CIT did not prevent WAY100,635 from raising extracellular 5-HT.
Ceglia, I; Acconcia, S; Fracasso, C; Colovic, M; Caccia, S; Invernizzi, R W
Parallel functional activity profiling reveals valvulopathogens are potent 5-hydroxytryptamine(2B) receptor agonists: implications for drug safety assessment.
Drug-induced valvular heart disease (VHD) is a serious side effect of a few medications, including some that are on the market. Pharmacological studies of VHD-associated medications (e.g., fenfluramine, pergolide, methysergide, and cabergoline) have revealed that they and/or their metabolites are potent 5-hydroxytryptamine(2B) (5-HT(2B)) receptor agonists. We have shown that activation of 5-HT(2B) receptors on human heart valve interstitial cells in vitro induces a proliferative response reminiscent of the fibrosis that typifies VHD. To identify current or future drugs that might induce VHD, we screened approximately 2200 U.S. Food and Drug Administration (FDA)-approved or investigational medications to identify 5-HT(2B) receptor agonists, using calcium-based high-throughput screening. Of these 2200 compounds, 27 were 5-HT(2B) receptor agonists (hits); 14 of these had previously been identified as 5-HT(2B) receptor agonists, including seven bona fide valvulopathogens. Six of the hits (guanfacine, quinidine, xylometazoline, oxymetazoline, fenoldopam, and ropinirole) are approved medications. Twenty-three of the hits were then "functionally profiled" (i.e., assayed in parallel for 5-HT(2B) receptor agonism using multiple readouts to test for functional selectivity). In these assays, the known valvulopathogens were efficacious at concentrations as low as 30 nM, whereas the other compounds were less so. Hierarchical clustering analysis of the pEC(50) data revealed that ropinirole (which is not associated with valvulopathy) was clearly segregated from known valvulopathogens. Taken together, our data demonstrate that patterns of 5-HT(2B) receptor functional selectivity might be useful for identifying compounds likely to induce valvular heart disease. PMID:19570945
Huang, Xi-Ping; Setola, Vincent; Yadav, Prem N; Allen, John A; Rogan, Sarah C; Hanson, Bonnie J; Revankar, Chetana; Robers, Matt; Doucette, Chris; Roth, Bryan L
Identification of 5-HT receptor subtypes enhancing inhibitory transmission in the rat spinal dorsal horn in vitro
Background 5-hydroxytryptamine (5-HT) is one of the major neurotransmitters widely distributed in the CNS. Several 5-HT receptor subtypes have been identified in the spinal dorsal horn which act on both pre- and postsynaptic sites of excitatory and inhibitory neurons. However, the receptor subtypes and sites of actions as well as underlying mechanism are not clarified rigorously. Several electrophysiological studies have been performed to investigate the effects of 5-HT on excitatory transmission in substantia gelatinosa (SG) of the spinal cord. In the present study, to understand the effects of 5-HT on the inhibitory synaptic transmission and to identify receptor subtypes, the blind whole cell recordings were performed from SG neurons of rat spinal cord slices. Results Bath applied 5-HT (50??M) increased the frequency but not amplitudes of spontaneous inhibitory postsynaptic currents (sIPSCs) in 58% of neurons, and both amplitude and frequency in 23% of neurons. The frequencies of GABAergic and glycinergic mIPSCs were both enhanced. TTX (0.5??M) had no effect on the increasing frequency, while the enhancement of amplitude of IPSCs was eliminated. Evoked-IPSCs (eIPSCs) induced by focal stimulation near the recording neurons in the presence of CNQX and APV were enhanced in amplitude by 5-HT. In the presence of Ba2+ (1?mM), a potassium channel blocker, 5-HT had no effect on both frequency and amplitude. A 5-HT2A receptor agonist, TCB-2 mimicked the 5-HT effect, and ketanserin, an antagonist of 5-HT2A receptor, inhibited the effect of 5-HT partially and TCB-2 almost completely. A 5-HT2C receptor agonist WAY 161503 mimicked the 5-HT effect and this effect was blocked by a 5-HT2C receptor antagonist, N-desmethylclozapine. The amplitudes of sIPSCs were unaffected by 5-HT2A or 5-HT2C agonists. A 5-HT3 receptor agonist mCPBG enhanced both amplitude and frequency of sIPSCs. This effect was blocked by a 5-HT3 receptor antagonist ICS-205,930. The perfusion of 5-HT2B receptor agonist had no effect on sIPSCs. Conclusions Our results demonstrated that 5-HT modulated the inhibitory transmission in SG by the activation of 5-HT2A and 5-HT2C receptors subtypes located predominantly at inhibitory interneuron terminals, and 5-HT3 receptors located at inhibitory interneuron terminals and soma-dendrites, consequently enhanced both frequency and amplitude of IPSCs.
Inverse agonist and neutral antagonist actions of synthetic compounds at an insect 5-HT1 receptor
Background and purpose: 5-Hydroxytryptamine (5-HT) has been shown to control and modulate many physiological and behavioural functions in insects. In this study, we report the cloning and pharmacological properties of a 5-HT1 receptor of an insect model for neurobiology, physiology and pharmacology. Experimental approach: A cDNA encoding for the Periplaneta americana 5-HT1 receptor was amplified from brain cDNA. The receptor was stably expressed in HEK 293 cells, and the functional and pharmacological properties were determined in cAMP assays. Receptor distribution was investigated by RT-PCR and by immunocytochemistry using an affinity-purified polyclonal antiserum. Key results: The P. americana 5-HT1 receptor (Pea5-HT1) shares pronounced sequence and functional similarity with mammalian 5-HT1 receptors. Activation with 5-HT reduced adenylyl cyclase activity in a dose-dependent manner. Pea5-HT1 was expressed as a constitutively active receptor with methiothepin acting as a neutral antagonist, and WAY 100635 as an inverse agonist. Receptor mRNA was present in various tissues including brain, salivary glands and midgut. Receptor-specific antibodies showed that the native protein was expressed in a glycosylated form in membrane samples of brain and salivary glands. Conclusions and implications: This study marks the first pharmacological identification of an inverse agonist and a neutral antagonist at an insect 5-HT1 receptor. The results presented here should facilitate further analyses of 5-HT1 receptors in mediating central and peripheral effects of 5-HT in insects.
Troppmann, B; Balfanz, S; Baumann, A; Blenau, W
The effects of 5-HT and m-chlorophenylpiperazine (m-CPP) on the efflux of [3H]-5-HT from human perfused platelets.
1. m-Chlorophenylpiperazine (m-CPP), a 5-HT1c-receptor agonist, induces migraine-like headaches when taken orally by migraine sufferers. The present study was undertaken to see what effects m-CPP had on 5-HT function in platelets. 2. Platelets from healthy male volunteers were loaded with [3H]-5-HT and continuously perfused in vitro with carboxygenated Krebs solution at 37 degrees C. After 30 min washout the effects of m-CPP, thrombin, 5-HT and ADP on the efflux of [3H]-5-HT were recorded. 3. m-CPP (0.5-500 microM) did not evoke an increase in the efflux of [3H]-5-HT over that occurring spontaneously whereas thrombin, unlabelled 5-HT and ADP did. The effects of 5-HT were potentiated by ADP. The results were identical whether or not the 5-HT reuptake blocker paroxetine (1 microM) was present. 4. m-CPP inhibited the increase in the efflux of [3H]-5-HT evoked by different concentrations of unlabelled 5-HT in the presence of ADP (2.5 microM) and displaced the 5-HT log concentration response curve to the right. A similar result was obtained with the 5-HT2-receptor antagonist ketanserin. 5. We conclude that m-CPP is a 5-HT2-receptor antagonist on human platelets, which is unlikely to account for its headache-inducing property, as many drugs effective in migraine prophylaxis have this action.
Carver, J G; Grahame-Smith, D G; Johnson, E S; Madgwick, Z
A 5-hydroxytryptamine receptor antagonist, sarpogrelate, reduces renal tubulointerstitial fibrosis by suppressing PAI-1.
A selective 5-hydroxytryptamine (5-HT) 2A receptor antagonist sarpogrelate (SG) blocks serotonin-induced platelet aggregation. It has been used clinically for the treatment of peripheral arterial disease. SG might be able to improve chronic ischemia, which contributes to renal fibrosis progression by maintaining renal microcirculation. This study investigated whether SG suppresses renal fibrosis. C57BL/6 mice fed a 0.2% adenine-containing diet for 6 wk developed severe tubulointerstitial fibrosis with kidney dysfunction. Subsequent SG treatment (30 mgĘkg(-1)Ęday(-1)) for 4 wk improved these changes significantly by increasing peritubular blood flow in the fibrotic area, as evaluated by intravital microscopy and decreasing fibrin deposition. Urinary L-type fatty acid-binding protein, up-regulated by renal hypoxia, was also reduced by SG. Additionally, results showed that mRNA expression of plasminogen activator inhibitor-1 (PAI-1), which is known to promote fibrosis by mediating and enhancing transforming growth factor (TGF)-?1 signaling, was suppressed by SG treatment in the kidney. In vitro experiments using cultured murine proximal tubular epithelial (mProx) cells revealed that incubation with TGF-?1 and 5-HT increased PAI-1 mRNA expression; SG significantly reduced it. In conclusion, SG reduces renal fibrosis not only by the antithrombotic effect of maintaining peritubular blood flow but also by suppressing PAI-1 expression in renal tubular cells. PMID:24107419
Hamasaki, Yoshifumi; Doi, Kent; Maeda-Mamiya, Rui; Ogasawara, Emi; Katagiri, Daisuke; Tanaka, Tamami; Yamamoto, Tokunori; Sugaya, Takeshi; Nangaku, Masaomi; Noiri, Eisei
Stimulation of 5-HT4 receptor enhances differentiation of mouse induced pluripotent stem cells into neural progenitor cells.
Activation of serotonin (5-hydroxytryptamine; 5-HT) receptors plays a role in adult neurogenesis and differentiation of neural progenitor cells (NPC). Herein, we examined the involvement of 5-HT receptors in the differentiation of mouse induced pluripotent stem (iPS) cells into NPC. To induce embryoid body (EB) formation, mouse iPS cells were cultured on ultralow-attachment dishes. All-trans retinoic acid (ATRA; 1Ā?mol/L) and/or 5-HT (0.03 or 0.1Ā?mol/L) was added to the EB cultures for 4Ādays and then EB plated on gelatin-coated plates were cultured for 7 or 14Ādays. Immunofluorescence staining revealed that mouse iPS cells expressed both 5-HT2A and 5-HT4 receptors and, to a lesser extent, 5-HT1A receptors. Treatment with 5-HT significantly enhanced the ATRA-induced expression of nestin, a specific marker for NPC, and phosphorylation of cAMP response element-binding protein (CREB). Pretreatment of EB cultures with either 1Ā?mol/L GR113808 (a selective 5-HT4 receptor antagonist) or 1Ā?mol/L H89 (a protein kinase (PKA) inhibitor) significantly inhibited these effects of 5-HT. These findings suggest that stimulation of 5-HT4 receptors may enhance ATRA-induced neural differentiation of mouse iPS cells through activation of PKA and CREB. PMID:24606396
Ishizuka, Toshiaki; Goshima, Hazuki; Ozawa, Ayako; Watanabe, Yasuhiro
5-HT(1A) receptor function in major depressive disorder.
Dysfunction of the serotonin 1A receptor (5-HT(1A)) may play a role in the genesis of major depressive disorder (MDD). Here we review the pharmacological, post-mortem, positron emission tomography (PET), and genetic evidence in support of this statement. We also touch briefly on two MDD-associated phenotypes, cognitive impairment and somatic pain. The results of pharmacological challenge studies with 5-HT(1A) receptor agonists are indicative of blunted endocrine responses in depressed patients. Lithium, valproate, selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), and other treatment, such as electroconvulsive shock therapy (ECT), all increase post-synaptic 5-HT(1A) receptor signaling through either direct or indirect effects. Reduced somatodendritic and postsynaptic 5-HT(1A) receptor numbers or affinity have been reported in some post-mortem studies of suicide victims, a result consistent with well-replicated PET analyses demonstrating reduced 5-HT(1A) receptor binding potential in diverse regions such as the dorsal raphe, medial prefrontal cortex (mPFC), amygdala and hippocampus. 5-HT(1A) receptor knockout (KO) mice display increased anxiety-related behavior, which, unlike in their wild-type counterparts, cannot be rescued with antidepressant drug (AD) treatment. In humans, the G allele of a single nucleotide polymorphism (SNP) in the 5-HT(1A) receptor gene (HTR1A; rs6295), which abrogates a transcription factor binding site for deformed epidermal autoregulatory factor-1 (Deaf-1) and Hes5, has been reported to be over-represented in MDD cases. Conversely, the C allele has been associated with better response to AD drugs. We raise the possibility that 5-HT(1A) receptor dysfunction represents one potential mechanism underpinning MDD and other stress-related disorders. PMID:19428959
Savitz, Jonathan; Lucki, Irwin; Drevets, Wayne C
Methylene blue inhibits function of the 5-HT transporter
BACKGROUND AND PURPOSE Methylene blue (MB) is commonly employed as a treatment for methaemoglobinaemia, malaria and vasoplegic shock. An increasing number of studies indicate that MB can cause 5-HT toxicity when administered with a 5-HT reuptake inhibitor. MB is a potent inhibitor of monoamine oxidases, but other targets that may contribute to MB toxicity have not been identified. Given the role of the 5-HT transporter (SERT) in the regulation of extracellular 5-HT concentrations, the present study aimed to characterize the effect of MB on SERT. EXPERIMENTAL APPROACH Live cell imaging, in conjunction with the fluorescent SERT substrate 4-(4-(dimethylamino)-styryl)-N-methylpyridinium (ASP+), [3H]5-HT uptake and whole-cell patch-clamp techniques were employed to examine the effects of MB on SERT function. KEY RESULTS In EM4 cells expressing GFP-tagged human SERT (hSERT), MB concentration-dependently inhibited ASP+ accumulation (IC50: 1.4 ▒ 0.3 ĄM). A similar effect was observed in N2A cells. Uptake of [3H]5-HT was decreased by MB pretreatment. Furthermore, patch-clamp studies in hSERT expressing cells indicated that MB significantly inhibited 5-HT-evoked ion currents. Pretreatment with 8-Br-cGMP did not alter the inhibitory effect of MB on hSERT activity, and intracellular Ca2+ levels remained unchanged during MB application. Further experiments revealed that ASP+ binding to cell surface hSERT was reduced after MB treatment. In whole-cell radioligand experiments, exposure to MB (10 ĄM; 10 min) did not alter surface binding of the SERT ligand [125I]RTI-55. CONCLUSIONS AND IMPLICATIONS MB modulated SERT function and suggested that SERT may be an additional target upon which MB acts to produce 5-HT toxicity.
Oz, Murat; Isaev, Dmytro; Lorke, Dietrich E; Hasan, Muhammed; Petroianu, Georg; Shippenberg, Toni S
Chronic stress-induced alterations in mouse colonic 5-HT and defecation responses are strain dependent.
Mood disorders and chronic stress are frequently associated with gastrointestinal (GI) symptoms including diarrhoea or constipation. Locally produced serotonin [5-hydroxytryptamine (5-HT)] regulates GI motility and is a key factor in the pathophysiology of stress-associated GI disorders. We aimed to establish whether chronic stress can differentially affect faecal output and colon 5-HT concentration in two inbred mouse strains: BALB/c and C57BL/6 which differ in their ability to cope with stress. Adult male BALB/c and C57BL/6 mice were restrained for 2Āh daily for 10 days. Defecation was monitored during each stress session. Twenty-four hours after the last session of stress, plasma corticosterone concentration was higher than control in both strains, indicative of a physiological effect of chronic stress; however, stress-induced diarrhoea was more persistent in C57BL/6 mice. Basal concentration of colon 5-HT was higher in C57BL/6 mice, and stress elicited an increase in colon 5-HT only in this strain. Finally, na've BALB/c mice had a higher sensitivity (incidence of diarrhoea) to 5-HT (0.33Āmg/kg, i.p.) than C57BL/6 mice. Our results suggest that differential defecation responses to stress may be associated with colon 5-HT concentration, which may in turn reflect the individual sensitivity to 5-HT. In addition, C57BL/6 mice emerge as a relevant model for studying GI alterations induced by chronic stress. PMID:21875301
Julio-Pieper, Marcela; O'Mahony, Cliona M; Clarke, Gerard; Bravo, Javier A; Dinan, Timothy G; Cryan, John F
Rapid desensitization and resensitization of 5-HT sub 2 receptor mediated phosphatidyl inositol hydrolysis by serotonin agonists in quiescent calf aortic smooth muscle cells
Agonist regulation of 5-hydroxytryptamine{sub 2} (5-HT{sub 2}) receptors was studied in calf aortic smooth muscle cultures incubated in a quiescent, defined synthetic medium that does not stimulate cell proliferation, but that provides cells with supplements that maintain cell viability. In these cells, 5-hydroxytryptamine (5-HT)-induced ({sup 3}H)inositol phosphates accumulation showed the characteristics of a 5-HT{sub 2} receptor coupled transducing system according to the inhibition of the response by 5-HT{sub 2} antagonists at nanomolar concentrations. The 5-HT{sub 2} receptor coupled response became rapidly desensitized during continued incubation with 5-HT and 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM); nearly full desensitization was obtained in two hours with 10 {mu}M 5-HT and DOM pretreatment. The recovery of the response had a half-live of 5 hours after 2 hours pretreatment and of 9.5 to 12.5 hours after 24 to 96 hours agonist pretreatment. The DOM-induced desensitization of the 5-HT{sub 2} receptor coupled response was fully blocked by 0.1 {mu}M cinanserin. Cinanserin alone did not induce desensitization or up-regulation of the 5-HT{sub 2} receptor coupled response at 0.1 {mu}M.
Pauwels, P.J.; Van Gompel, P.; Leysen, J.E. (Janssen Research Foundation, Beerse (Belgium))
Backward walking and circling: behavioural responses induced by drug treatments which cause simultaneous release of catecholamines and 5-hydroxytryptamine.
1 The roles of catecholamine and 5-hydroxytryptamine (5-HT) release in mediating backward walking and circling were studied in rats. 2 These behaviours occurred in animals given 15 mg/kg intraperitoneally of (+)-amphetamine (which predominantly releases catecholamines) or either p-chloroamphetamine or fenfluramine (which predominantly release 5-HT). They also occurred when smaller doses of (+)-amphetamine (5 mg/kg) and either p-chloroamphetamine (2--5 mg/kg) or fenfluramine (5 mg/kg) were given together. 3 Characteristic dopamine-dependent behaviours (rearing, licking, gnawing) resulting from (+)-amphetamine injection were greatly reduced by p-chloroamphetamine or fenfluramine. 4 Characteristic 5-HT-dependent behaviours (wet dog shake, hind limb abduction) resulting from injection of either p-chloroamphetamine or fenfluramine were unaffected by (+)-amphetamine. 5 Fragmentary backward walking and circling resulting from levallorphan injection (50 mg/kg s.c.) were decreased by (+)-amphetamine at low dosage. 6 Results in general strengthen previous evidence that backward walking and circling are mediated by simultaneous dopamine and 5-HT release. 7 The possible relevance of the above findings to hallucinogenic activity, amphetamine psychosis, schizophrenia and abnormal movements due to L-DOPA treatment is discussed.
Curzon, G.; Fernando, J. C.; Lees, A. J.
Modulation of I H by 5HT in Neonatal Rat Motoneurones In Vitro: Mediation through a Phosphorylation Independent Action of cAMP
The depolarization of adult and neonatal rat facial and spinal motoneurones by 5-hydroxytryptamine (5-HT) in part involves an enhancement of the hyperpolarization-activated, inward-rectifier, IH. Under experimental conditions which promote this action, 5-HT evokes an inward current which can be mimicked by intracellularly applied adenosine 3?:5?-cyclic monophosphate (cAMP) and potentiated by the cAMP-specific phosphodiesterase inhibitor Ro 20-1724. In this study, we
A 5HT7 Receptor-Mediated Depolarization in the Anterodorsal Thalamus. II. Involvement of the Hyperpolarization-Activated Current Ih
Previous studies have shown that 5-hydroxytryptamine (5-HT) can modulate the hyperpolarization-activated nonselective cat- ion current (Ih) to elicit a membrane depolarization in neurons. However, the receptor subtype involved in this response re- mains controversial. In the accompanying study, we have iden- tified a 5-HT7 receptor-mediated depolarization in the an- terodorsal nucleus of the thalamus (ADn). In the present study, we
Effect of acute and prolonged tianeptine administration on the 5HT transporter: electrophysiological, biochemical and radioligand binding studies in the rat brain
In the present study, in vivo extracellular unitary recordings, in vitro [3H]5-HT uptake and [3H]cyanoimipramine binding assays were used to assess the effect of acute and prolonged administration of the putative antidepressant tianeptine, on the 5-hydroxytryptamine (5-HT) transporter. Microiontophoretic application of tianeptine onto dorsal hippocampus CA3 pyramidal neurons, as well as its intravenous administration (2 mg\\/kg), increased their firing frequency.
Graciela Pi±eyro; Lyne Deveault; Pierre Blier; Trevor Dennis; Claude Montigny
Circadian variation in the distribution of Hymenolepis diminuta (Cestoda) and 5-hydroxytryptamine levels in the gastro-intestinal tract of the laboratory rat.
The circadian migration of Hymenolepis diminuta in the small intestine of the rat may be correlated with a circadian variation in 5-hydroxytryptamine levels present in worm tissue, in the intestinal lumen, in the intestinal mucosa, with the amount of fold present in the small intestine and in arterial blood. 5-HT and food levels in uninfected animals were also determined. The 16.00 h stage in the circadian cycle marks both the commencement of host feeding, followed by rising 5-HT levels in both worm and host tissues, and initiation of an anteriad migration of worm biomass. It was found that 5-HT levels in the intestine of parasitized animals were significantly higher than in the intestine of uninfected controls. This is the first report of circadian variation in mucosal and luminal 5-HT levels. The similarity in the circadian patterns of worm migration and worm luminal, mucosal and blood 5-HT levels were striking. Fasting eliminated the circadian rise in intestinal 5-HT levels and the worms did not migrate. Luminal 5-HT levels were significantly lower in fasted animals than in the comparable rats fed ad libitum. When the intestine was ligatured at the pyloric sphincter, worm anteriad migration still occurred after feeding, indicating that the presence of exogenous food in the intestine is not a factor in the initial migration of the worms. PMID:7099709
Cho, C H; Mettrick, D F
Silencing of p21-activated kinase attenuates vimentin phosphorylation on Ser-56 and reorientation of the vimentin network during stimulation of smooth muscle cells by 5-hydroxytryptamine
Vimentin intermediate filaments undergo spatial reorganization in endothelial cells and fibroblasts in response to stimulation with platelet-derived growth factor and epidermal growth factor. In the present study, the vimentin network exhibited a curved filamentous structure in unstimulated smooth muscle cells. Vimentin filaments became straight and were arranged along the long axis of cells upon stimulation with 5-hydroxytryptamine (5-HT; serotonin). Stimulation of smooth muscle cells with 5-HT also induced phosphorylation of vimentin on Ser-56. Treatment of cells with small interfering RNA selectively down-regulated the expression of PAK1 (p21-activated kinase 1) without affecting the content of smooth muscle ?-actin. The silencing of PAK1 inhibited the site-specific phosphorylation and spatial rearrangement of the vimentin network in response to stimulation with 5-HT. Neither the disruption of stress fibres by cytochalasin D nor the inhibition of protein tyrosine phosphorylation affects the spatial reorganization of vimentin intermediate filaments in response to stimulation with 5-HT. In addition, stimulation of smooth muscle cells with 5-HT increased the ratio of soluble to insoluble vimentin. PAK1 silencing attenuated increases in the ratio of soluble to insoluble vimentin upon stimulation with 5-HT. These results suggest that the PAK-mediated site-specific phosphorylation of vimentin may play a role in regulating the reorganization of vimentin intermediate filaments during stimulation of smooth muscle cells with 5-HT.
Actions of the 5-hydroxytryptamine 1 receptor agonist sumatriptan on interdigestive gastrointestinal motility in man
BackgroundŚPharmacological studies of the enteric nervous system have shown the presence of several subtypes of 5-hydroxytryptamine (5HT) receptor, which might be involved in control of the migrating motor complex. ?AimsŚTo study the effect of sumatriptan, an agonist of enteric neuronal 5HT1P receptors, on interdigestive motility in man. ?Subjects and methodsŚIn 12 healthy subjects, interdigestive motility was recorded manometrically in the upper gastrointestinal tract. In seven subjects blood samples were drawn every 15 minutes for radioimmunoassay of motilin and somatostatin. After two phase 3s of the migrating motor complex, 6 mg of sumatriptan was administered subcutaneously. Recording continued until two more phase 3s had occurred. ?ResultsŚSumatriptan induced a premature phase 3 in the jejunum after a median of 10 (8) minutes. The duration of the migrating motor complex cycle was shortened at the expense of phase 2. After sumatriptan, plasma somatostatin concentrations were reduced and gastric phase 3s were suppressed, although median motilin concentrations and the occurrence of plasma motilin peaks were not affected. Phase 3s of the migrating motor complex preceding sumatriptan were associated with motilin peaks, while phase 3s after sumatriptan were not. Furthermore, pretreatment with sumatriptan prevented the induction of a gastric phase 3 by the motilin agonist erythromycin. ?ConclusionsŚAdministration of the 5HT1P receptor agonist sumatriptan induces a premature intestinal phase 3, suppresses gastric phase 3s, prevents induct- ion of a gastric phase 3 by erythromycin, and reduces plasma somatostatin concentrations. ?? Keywords: migrating motor complex; motilin; somatostatin; erythromycin; enteric nervous system
Tack, J; Coulie, B; Wilmer, A; Peeters, T; Janssens, J
Emesis and Defecations Induced by the 5-Hydroxytryptamine (5-HT3) Receptor Anatagonist Zacopride in the Ferret.
National Technical Information Service (NTIS)
Three antiemetic compounds (zacopride, batanopride, granisetron were evaluated for the production of gastrointestinal side effects in the conscious ferret after i.v. or p.o. administration. Zacopride evoked multiple emetic and defecatory responses at clin...
G. L. King
Radioligand binding analysis of knockout mice reveals 5-hydroxytryptamine(7) receptor distribution and uncovers 8-hydroxy-2-(di-n-propylamino)tetralin interaction with alpha(2) adrenergic receptors.
In the present autoradiographic study, we took advantage of 5-hydroxytryptamine(7) (5-HT(7)) receptor knockout mice to analyze the brain distribution of 5-HT(7) receptor binding sites using [(3)H]5-carboxamidotryptamine (5-CT; a 5-HT(1A/1B/1D/5/7) receptor ligand) and [(3)H]8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; a 5-HT(1A/7) receptor ligand). Low to moderate densities of [(3)H]5-CT (2 nM) binding sites insensitive to pindolol (10 microM, for 5-HT(1A/1B) receptor blockade) and GR-127935 (1 microM; for 5-HT(1D) receptor blockade) were observed in wild-type mice (mainly in thalamus and hypothalamus) but not in 5-HT(7) receptor knockout mice. Surprisingly, moderate to high densities of [(3)H]8-OH-DPAT (10 nM) binding sites insensitive to pindolol (10 microM) remained in 5-HT(7) receptor knockout mouse brain. These non-5-HT(1A), non-5-HT(7) binding sites were found to be adrenergic alpha(2A) receptor binding sites. In alpha(2A) receptor knockout mice low to moderate densities of [(3)H]8-OH-DPAT binding sites insensitive to pindolol but sensitive to the selective 5-HT(7) receptor antagonist SB-269970 (300 nM) were observed mainly in thalamus and hypothalamus. Therefore, in addition to 5-HT(1A) and 5-HT(7) binding sites, [(3)H]8-OH-DPAT also binds to alpha(2A) receptor binding sites in wild-type mouse brain. [(3)H]8-OH-DPAT (in the presence of pindolol and 1 microM RX-821002 for alpha(2) receptor blockade) and [(3)H]5-CT (in the presence of pindolol and GR-127935) bind to a similar receptor binding population corresponding to 5-HT(7) binding sites. Detailed anatomical mapping of 5-HT(7) receptor binding sites in wild-type mouse brain was then performed using both radioligands in the presence of suitable pharmacological agents for non-5-HT(7) receptor binding sites blockade. The mapping revealed binding sites consistent with the mRNA distribution with the highest densities found in anterior thalamic nuclei. PMID:15026130
Bonaventure, P; Nepomuceno, D; Hein, L; Sutcliffe, J G; Lovenberg, T; Hedlund, P B
Glucose-dependent trafficking of 5-HT3 receptors in rat gastrointestinal vagal afferent neurons
Background Intestinal glucose induces gastric relaxation via vagally mediated sensory-motor reflexes. Glucose can alter the activity of gastrointestinal (GI) vagal afferent (sensory) neurons directly, via closure of ATP-sensitive potassium channels, as well as indirectly, via the release of 5-hydroxytryptamine (5-HT) from mucosal enteroendocrine cells. We hypothesized that glucose may also be able to modulate the ability of GI vagal afferent neurons to respond to the released 5-HT, via regulation of neuronal 5-HT3 receptors. Methods Whole cell patch clamp recordings were made from acutely dissociated GI-projecting vagal afferent neurons exposed to equiosmolar KrebsÆ solution containing different concentrations of D-glucose (1.25¢20mM) and the response to picospritz application of 5-HT assessed. The distribution of 5-HT3 receptors in neurons exposed to different glucose concentrations was also assessed immunohistochemically. Key Results Increasing or decreasing extracellular D-glucose concentration increased or decreased, respectively, the 5-HT-induced inward current as well as the proportion of 5-HT3 receptors associated with the neuronal membrane. These responses were blocked by the Golgi-disrupting agent Brefeldin-A (5ĄM) suggesting involvement of a protein trafficking pathway. Furthermore, L-glucose did not mimic the response of D-glucose implying that metabolic events downstream of neuronal glucose uptake are required in order to observe the modulation of 5-HT3 receptor mediated responses. Conclusions & Inferences These results suggest that, in addition to inducing the release of 5-HT from enterochromaffin cells, glucose may also increase the ability of GI vagal sensory neurons to respond to the released 5-HT, providing a means by which the vagal afferent signal can be amplified or prolonged.
Babic, Tanja; Troy, Amanda E; Fortna, Samuel R; Browning, Kirsteen N
From obesity to substance abuse: therapeutic opportunities for 5-HT2C receptor agonists.
The recent US Food and Drug Administration (FDA) approval of the serotonin (5-hydroxytryptamine, 5-HT) 5-HT2C receptor agonist lorcaserin for the treatment of obesity represents a new therapeutic drug class available to the clinic. Preclinical evidence supports the potential for this drug class to treat other related conditions such as substance abuse. In the present article we review this evidence and further suggest that overlapping neurobiological systems may contribute to an anti-addictive and anti-obesity profile. The availability of selective 5-HT2C agonists provides an opportunity to evaluate their potential as treatments for nicotine dependence or psychostimulant abuse, conditions for which there is significant medical need but only limited available treatment options. PMID:24041919
Higgins, Guy A; Sellers, Edward M; Fletcher, Paul J
Serotonin (5-HT) regulates neurite outgrowth through 5-HT1A and 5-HT7 receptors in cultured hippocampal neurons.
Serotonin (5-HT) production and expression of 5-HT receptors (5-HTRs) occur early during prenatal development. Recent evidence suggests that, in addition to its classical role as a neurotransmitter, 5-HT regulates neuronal connectivity during mammalian development by modulating cell migration and neuronal cytoarchitecture. Given the variety of 5-HTRs, researchers have had difficulty clarifying the specific role of each receptor subtype in brain development. Signalling mediated by the G-protein-coupled 5-HT1A R and 5-HT7 R, however, has been associated with neuronal plasticity. Thus, we hypothesized that 5-HT promotes neurite outgrowth through 5-HT1A R and 5-HT7 R. The involvement of 5-HT1A R and 5-HT7 R in the morphology of rat hippocampal neurons was evaluated by treating primary cultures at 2 days in vitro with 5-HT and specific antagonists for 5-HT1A R and 5-HT7 R (WAY-100635 and SB269970, respectively). The stimulation of hippocampal neurons with 100 nM 5-HT for 24 hr produced no effect on either the number or the length of primary neurites. Nonetheless, after 5HT7 R was blocked, the addition of 5-HT increased the number of primary neurites, suggesting that 5HT7 R could inhibit neuritogenesis. In contrast, 5-HT induced secondary neurite outgrowth, an effect inhibited by 1 ?M WAY-100635 or SB269970. These results suggest that both serotonergic receptors participate in secondary neurite outgrowth. We conclude that 5-HT1A R and 5-HT7 R regulate neuronal morphology in primary hippocampal cultures by promoting secondary neurite outgrowth. ® 2014 Wiley Periodicals, Inc. PMID:24752854
Rojas, Paulina S; Neira, David; Mu±oz, Mauricio; Lavandero, Sergio; Fiedler, Jenny L
5-HT2C Receptor Agonist Anorectic Efficacy Potentiated by 5-HT1B Receptor Agonist Coapplication: An Effect Mediated via Increased Proportion of Pro-Opiomelanocortin Neurons Activated
An essential component of the neural network regulating ingestive behavior is the brain 5-hydroxytryptamine2C receptor (5-HT2CR), agonists of which suppress food intake and were recently approved for obesity treatment by the US Food and Drug Administration. 5-HT2CR-regulated appetite is mediated primarily through activation of hypothalamic arcuate nucleus (ARC) pro-opiomelanocortin (POMC) neurons, which are also disinhibited through a 5-HT1BR-mediated suppression of local inhibitory inputs. Here we investigated whether 5-HT2CR agonist anorectic potency could be significantly enhanced by coadministration of a 5-HT1BR agonist and whether this was associated with augmented POMC neuron activation on the population and/or single-cell level. The combined administration of subanorectic concentrations of 5-HT2CR and 5-HT1BR agonists produced a 45% reduction in food intake and significantly greater in vivo ARC neuron activation in mice. The chemical phenotype of activated ARC neurons was assessed by monitoring agonist-induced cellular activity via calcium imaging in mouse POMC-EGFP brain slices, which revealed that combined agonists activated significantly more POMC neurons (46%) compared with either drug alone (~25% each). Single-cell electrophysiological analysis demonstrated that 5-HT2CR/5-HT1BR agonist coadministration did not significantly potentiate the firing frequency of individual ARC POMC-EGFP cells compared with agonists alone. These data indicate a functional heterogeneity of ARC POMC neurons by revealing distinct subpopulations of POMC cells activated by 5-HT2CRs and disinhibited by 5-HT1BRs. Therefore, coadministration of a 5-HT1BR agonist potentiates the anorectic efficacy of 5-HT2CR compounds by increasing the number, but not the magnitude, of activated ARC POMC neurons and is of therapeutic relevance to obesity treatment.
Doslikova, Barbora; Garfield, Alastair S.; Shaw, Jill; Evans, Mark L.; Burdakov, Denis; Billups, Brian; Heisler, Lora K.
Activation of the 5-HT4 receptor mediates widespread effects in central and peripheral nervous systems. Recent developments, such as the identification of novel, selective agonists and antagonists, as well the cloning of the receptor, have provided insights into the physiological role of the receptor. In this article, Richard Eglen and colleagues assess the emerging evidence relating to the function of the
Aline Dumuis; Joļl Bockaert
Gaddum and LSD: the birth and growth of experimental and clinical neuropharmacology research on 5-HT in the UK
The vasoconstrictor substance named serotonin was identified as 5-hydroxytryptamine (5-HT) by Maurice Rapport in 1949. In 1951, Rapport gave Gaddum samples of 5-HT substance allowing him to develop a bioassay to both detect and measure the amine. Gaddum and colleagues rapidly identified 5-HT in brain and showed that lysergic acid diethylamide (LSD) antagonized its action in peripheral tissues. Gaddum accordingly postulated that 5-HT might have a role in mood regulation. This review examines the role of UK scientists in the first 20 years following these major discoveries, discussing their role in developing assays for 5-HT in the CNS, identifying the enzymes involved in the synthesis and metabolism of 5-HT and investigating the effect of drugs on brain 5-HT. It reviews studies on the effects of LSD in humans, including Gaddum's self-administration experiments. It outlines investigations on the role of 5-HT in psychiatric disorders, including studies on the effect of antidepressant drugs on the 5-HT concentration in rodent and human brain, and the attempts to examine 5-HT biochemistry in the brains of patients with depressive illness. It is clear that a rather small group of both preclinical scientists and psychiatrists in the UK made major advances in our understanding of the role of 5-HT in the brain, paving the way for much of the knowledge now taken for granted when discussing ways that 5-HT might be involved in the control of mood and the idea that therapeutic drugs used to alleviate psychiatric illness might alter the function of cerebral 5-HT.
Green, A R
Peripheral 5-HT2-like receptors. Can they be classified with the available antagonists?
Interactions between 5-hydroxytryptamine (5-HT) and the so-called 5-HT2 receptor antagonists ketanserin, spiperone, trazodone and methysergide were studied in isolated preparations of the rabbit aorta, rat jugular vein, and rat caudal artery. Trazodone and spiperone were apparently simple competitive antagonists since they produced antagonism that was surmountable over the concentration range studied and, in each tissue, their apparent affinity appeared to be independent of the antagonist concentration. Furthermore, concentration-ratios obtained with the two antagonists in combination suggested that antagonism was additive, implying mutual competition with a single population of 5-HT receptors. Ketanserin was a non-surmountable antagonist of 5-HT in the rat caudal artery and methysergide demonstrated surmountable, competitive antagonism only in the rabbit aorta. Antagonist dissociation constants estimated for apparently competitive interactions showed that ketanserin, spiperone and trazodone expressed affinities which differed according to the tissue used. In the case of trazodone, affinity estimates differed by as much as 12 fold. These discrepancies were independent of the 5-HT receptor agonist used and could not be attributed to an inadequate equilibration of the antagonist. These results can be interpreted in two ways: either the receptors in the different tissues are heterogeneous or the antagonists used here must be considered as unreliable probes for the classification of 5-HT2-like receptors.
Leff, P.; Martin, G. R.
Effects of treatment with a 5-HT4 receptor antagonist in heart failure
Background and purpose: Positive inotropic responses (PIR) to 5-hydroxytryptamine (5-HT) are induced in the left ventricle (LV) in rats with congestive heart failure (CHF); this is associated with upregulation of the Gs-coupled 5-HT4 receptor. We investigated whether chronic 5-HT4 receptor blockade improved cardiac function in CHF rats. Experimental approach: Rats were given either the 5-HT4 antagonist SB207266 (0.5?mg kg?1 24h?1; MIint) or placebo (MIpl) through mini-osmotic pumps for 6 weeks subsequent to induction of post-infarction CHF. In vivo cardiac function and ex vivo responses to isoprenaline or 5-HT were evaluated using echocardiography and isolated LV papillary muscles, respectively. mRNA levels were investigated using real-time quantitative RT-PCR. Key results: LV diastolic function improved, with 4.6% lower LV diastolic diameter and 24.2% lower mitral flow deceleration in MIint compared to MIpl. SB207266 reduced LV systolic diameter by 6.1%, heart weight by 10.2% and lung weight by 13.1%. The changes in posterior wall thickening and shortening velocity, cardiac output, LV systolic pressure and (dP/dt)max, parameters of LV systolic function, did not reach statistical significance. The PIR to isoprenaline (10 ?M) increased by 36% and the response to 5-HT (10 ?M) decreased by 57% in MIint compared to MIpl. mRNA levels for ANP, 5-HT4(b) and 5-HT2A receptors, MHC?, and the MHC?/MHC? -ratio were not significantly changed in MIint compared to MIpl. Conclusions and implications: Treatment with SB207266 to some extent improved in vivo cardiac function and ex vivo myocardial function, suggesting a possible beneficial effect of treatment with a 5-HT4 receptor antagonist in CHF.
Birkeland, J A K; Sjaastad, I; Brattelid, T; Qvigstad, E; Moberg, E R; Krobert, K A; Bj?rnerheim, R; Skomedal, T; Sejersted, O M; Osnes, J-B; Levy, F O
Prophylaxis of Radiation-Induced Nausea and Vomiting Using 5-Hydroxytryptamine-3 Serotonin Receptor Antagonists: A Systematic Review of Randomized Trials
Purpose: To systematically review the effectiveness and safety of 5-hydroxytryptamine-3 receptor antagonists (5-HT3 RAs) compared with other antiemetic medication or placebo for prophylaxis of radiation-induced nausea and vomiting. Methods and Materials: We searched the following electronic databases: MEDLINE, Embase, the Cochrane Central Register of Controlled Clinical Trials, and Web of Science. We also hand-searched reference lists of included studies. Randomized, controlled trials that compared a 5-HT3 RA with another antiemetic medication or placebo for preventing radiation-induced nausea and vomiting were included. We excluded studies recruiting patients receiving concomitant chemotherapy. When appropriate, meta-analysis was conducted using Review Manager (v5) software. Relative risks were calculated using inverse variance as the statistical method under a random-effects model. We assessed the quality of evidence by outcome using the Grading of Recommendations Assessment, Development, and Evaluation approach. Results: Eligibility screening of 47 articles resulted in 9 included in the review. The overall methodologic quality was moderate. Meta-analysis of 5-HT3 RAs vs. placebo showed significant benefit for 5-HT3 RAs (relative risk [RR] 0.70; 95% confidence interval [CI] 0.57-0.86 for emesis; RR 0.84, 95% CI 0.73-0.96 for nausea). Meta-analysis comparing 5-HT3 RAs vs. metoclopramide showed a significant benefit of the 5-HT3 RAs for emetic control (RR 0.27, 95% CI 0.15-0.47). Conclusion: 5-Hydroxytryptamine-3 RAs are superior to placebo and other antiemetics for prevention of emesis, but little benefit was identified for nausea prevention. 5-Hydroxytryptamine-3 RAs are suggested for prevention of emesis. Limited evidence was found regarding delayed emesis, adverse events, quality of life, or need for rescue medication. Future randomized, controlled trials should evaluate different 5-HT3 antiemetics and new agents with novel mechanisms of action such at the NK{sub 1} receptor antagonists to determine the most effective drug. Delayed nausea and vomiting should be a focus of future study, perhaps concentrating on the palliative cancer population.
Salvo, Nadia; Doble, Brett [Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario (Canada); Khan, Luluel [Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Amirthevasar, Gayathri [Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario (Canada); Dennis, Kristopher [Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Pasetka, Mark; DeAngelis, Carlo [Department of Oncology Pharmacy, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Tsao, May [Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Chow, Edward, E-mail: firstname.lastname@example.com [Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada)
Kinetic modeling of the serotonin 5HT1B receptor radioligand [11C]P943 in humans
[11C]P943 is a new radioligand recently developed to image and quantify serotonin 5-Hydroxytryptamine (5-HT1B) receptors with positron emission tomography (PET). The purpose of this study was to evaluate [11C]P943 for this application in humans, and to determine the most suitable quantification method. Positron emission tomography data and arterial input function measurements were acquired in a cohort of 32 human subjects.
Jean-Dominique Gallezot; Nabeel Nabulsi; Alexander Neumeister; Beata Planeta-Wilson; Wendol A Williams; Tarun Singhal; Sunhee Kim; R Paul Maguire; Timothy McCarthy; J James Frost; Yiyun Huang; Yu-Shin Ding; Richard E Carson; J-D Gallezot
Antagonism by the 5HT 2A\\/C receptor agonist DOI of raclopride-induced catalepsy in the rat
It has been shown that the administration of 5-hydroxytryptamine (5-HT)1A receptor agonists will antagonize the catalepsy induced by dopamine D1 or D2 receptor blocking agents. In the present study, administration of the 5-HT2A\\/C receptor agonist, 1-(2,5-dimethoxy-4-iodo)-2-aminopropane (DOI) (1 mg kg?1 s.c.), counteracted the catalepsy produced by the dopamine D2 receptor antagonist, raclopride (16 mg kg?1 s.c.), but not by the
Marie-Louise Wadenberg; Sven Ahlenius
DR4004, a putative 5HT 7 receptor antagonist, also has functional activity at the dopamine D2 receptor
The tetrahydrobenzindole, 2a-(4-(4-phenyl-1,2,3,6-tetrahydropyridyl)butyl)-2a,3,4,5-tetrahydrobenzo[cd]indol-2(1H)-one (DR4004) has been described as a highly selective antagonist for the 5-hydroxytryptamine7 (5-HT7) receptor [J. Med. Chem. 42 (1999) 533]. Consistent with original data, DR4004 bound to rat hypothalamic membranes with an affinity of 7.3▒0.2 (pKi▒S.E.M.) for the 5-HT7 receptor. However, competition binding studies showed that DR4004 had poor receptor selectivity with the following affinity profile; dopamine
Helen A Kogan; Charles A Marsden; Kevin C. F Fone
Agonism of the 5-Hydroxytryptamine 1F Receptor Promotes Mitochondrial Biogenesis and Recovery from Acute Kidney Injury.
Many acute and chronic conditions, such as acute kidney injury, chronic kidney disease, heart failure, and liver disease, involve mitochondrial dysfunction. Although we have provided evidence that drug-induced stimulation of mitochondrial biogenesis (MB) accelerates mitochondrial and cellular repair, leading to recovery of organ function, only a limited number of chemicals have been identified that induce MB. The goal of this study was to assess the role of the 5-hydroxytryptamine 1F (5-HT1F) receptor in MB. Immunoblot and quantitative polymerase chain reaction analyses revealed 5-HT1F receptor expression in renal proximal tubule cells (RPTC). A MB screening assay demonstrated that two selective 5-HT1F receptor agonists, LY334370 (4-fluoro-N-[3-(1-methyl-4-piperidinyl)-1H-indol-5-yl]benzamide) and LY344864 (N-[(3R)-3-(dimethylamino)-2,3,4,9-tetrahydro-1H-carbazol-6-yl]-4-fluorobenzamide; 1-100 nM) increased carbonylcyanide-p-trifluoromethoxyphenylhydrazone-uncoupled oxygen consumption in RPTC, and validation studies confirmed both agonists increased mitochondrial proteins [e.g., ATP synthase ?, cytochrome c oxidase 1 (Cox1), and NADH dehydrogenase (ubiquinone) 1? subcomplex subunit 8 (NDUFB8)] in vitro. Small interfering RNA knockdown of the 5-HT1F receptor blocked agonist-induced MB. Furthermore, LY344864 increased peroxisome proliferator-activated receptor coactivator 1-?, Cox1, and NDUFB8 transcript levels and mitochondrial DNA (mtDNA) copy number in murine renal cortex, heart, and liver. Finally, LY344864 accelerated recovery of renal function, as indicated by decreased blood urea nitrogen and kidney injury molecule 1 and increased mtDNA copy number following ischemia/reperfusion-induced acute kidney injury (AKI). In summary, these studies reveal that the 5-HT1F receptor is linked to MB, 5-HT1F receptor agonism promotes MB in vitro and in vivo, and 5-HT1F receptor agonism promotes recovery from AKI injury. Induction of MB through 5-HT1F receptor agonism represents a new target and approach to treat mitochondrial organ dysfunction. PMID:24849926
Garrett, Sara M; Whitaker, Ryan M; Beeson, Craig C; Schnellmann, Rick G
Evidence for an involvement of 5HT1B receptors in the inhibition of male rat ejaculatory behavior produced by 5HTP
The administration of the 5-hydroxytryptamine (5-HT) precursor 5hydroxytryptophan (5-HTP) (25mg\\/kg IP), in combination with\\u000a an inhibitor of peripheral 5-HTP decarboxylase, produced a dose-dependent increase in the ejaculation latency of male rats,\\u000a and this effect was enhanced by additional treatment with the 5-HT1 receptor antagonist (?)-pindolol (2mg\\/kg SC). The 5-HT2A\\/C receptor agonist ()1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (0.125¢0.5mg\\/kg SC) did not by itself affect
S. Ahlenius; Knut Larsson
The behavioural responses to 8-OH-DPAT, ipsapirone and the novel 5HT1A receptor agonist Bay Vq 7813 in the pig
In pigs, behavioural responses were examined after administration of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a full agonist at 5-hydroxytryptamine (5-HT) receptors of the 5-HT1A subtype, and the pyrimidinylpiperazine derivatives ipsapirone and Bay Vq 7813 (2-[4-(2-pyrimidinyl)-1-piperazinylpropyl]-1,2-benzisothiazol-3(2H)one-1,1-dioxide), which act as partial agonists at 5-HT1A receptors. The most prominent behavioural response examined after 8-OH-DPAT, 0.5 mg\\/kg i. m., ipsapirone, 2¢5 mg\\/kg i.m., and Bay Vq 7813,
Wolfgang L÷scher; Ulrike Witte; Gabriele Fredow; J÷rg Traber; Thomas Glaser
Time trial performance in normal and high ambient temperature: is there a role for 5HT?
The original central fatigue hypothesis suggested that fatigue during prolonged exercise might be due to higher 5-HT activity.\\u000a Therefore, we examined the effects of acute administration of a selective 5-HT reuptake inhibitor (SSRI) on performance and\\u000a thermoregulation. Eleven healthy trained male cyclists completed four experimental trials (two in 18░C, two in 30░C) in a\\u000a double-blind randomised crossover design. Subjects ingested
Bart Roelands; Maaike Goekint; Luk Buyse; Frank Pauwels; Guy De Schutter; Francesca Piacentini; Hiroshi Hasegawa; Phil Watson; Romain Meeusen
Byssinosis: Release of prostaglandins, thromboxane, and 5-hydroxytryptamine in bronchopulmonary lavage fluid after inhalation of cotton dust extracts.
New Zealand White rabbits were exposed intratracheally to aerosolized cotton dust extract (CDE) for 5 minutes of tidal breathing and lavaged 15 minutes 1, 4, and 6 hours after exposure. Bronchoalveolar lavage cells were counted, and the number of macrophages and polymorphonuclear leukocytes (PMNs) was determined. Cell recruitment, which began 1 hour after exposure to CDE and plateaued at 6 hours, consisted of both mononuclear cells and PMNs. Lavage fluid was analyzed for concentrations of prostaglandin F2 alpha (PGF2 alpha), prostaglandin E1 and E2 (PGE), thromboxane B2 (TxB2), and 5-hydroxytryptamine (5-HT). PGF2 alpha, PGE, TxB2, and 5-HT were maximally increased in the lavage 4 hours after exposure to CDE. This is the first study to demonstrate the in vivo release of arachidonic acid metabolites and 5-HT in the lung in response to CDE inhalation. This study also demonstrates that maximum mediator release occurs at 4 hours after exposure to aerosolized CDE. These findings strongly suggest that arachidonic acid metabolites are available to mediate either totally or partially the pathogenic mechanism(s) of bronchoconstriction seen in the acute byssinotic reaction of man.
Mundie, T. G.; Whitener, C.; Ainsworth, S. K.
Functional evidence for the rapid desensitization of 5-HT(3) receptors on vagal afferents mediating the Bezold-Jarisch reflex
NASA Technical Reports Server (NTRS)
The aim of this study was to determine whether 5-hydroxytryptamine (5-HT)(3) receptors on cardiopulmonary afferents mediating the Bezold-Jarisch reflex (BJR) desensitize upon repeated exposure to selective agonists. BJR-mediated falls in heart rate, diastolic arterial blood pressure and cardiac output elicited by the 5-HT(3)-receptor agonists, phenylbiguanide (100 microg/kg, i.v.) or 2-methyl-5-HT (100 microg/kg, i.v.), progressively diminished upon repeated injection in conscious rats. The BJR responses elicited by 5-HT (40 microg/kg, i.v.) were markedly reduced in rats which had received the above injections of phenylbiguanide or 2-methyl-5-HT whereas the BJR responses elicited by L-S-nitrosocysteine (10 micromol/kg, i.v.) were similar before and after the injections of the 5-HT(3) receptor agonists. These findings suggest that tachyphylaxis to 5-HT(3) receptor agonists may be due to the desensitization of 5-HT(3) receptors on cardiopulmonary afferents rather than the impairment of the central or peripheral processing of the BJR.
Whalen, E. J.; Johnson, A. K.; Lewis, S. J.
Postnatal maintenance of the 5-Ht1a-Pet1 autoregulatory loop by serotonin in the raphe nuclei of the brainstem
Background Despite the importance of 5-HT1A as a major target for the action of several anxiolytics/antidepressant drugs, little is known about its regulation in central serotonin (5-hydroxytryptamine, 5-HT) neurons. Results We report that expression of 5-HT1A and the transcription factor Pet1 was impaired in the rostral raphe nuclei of mice lacking tryptophan hydroxylase 2 (Tph2) after birth. The downregulation of Pet1 was recapitulated in 5-Ht1a -/- mice. Using an explant culture system, we show that reduction of Pet1 and 5-HT1A was rescued in Tph2 -/- brainstem by exogenous 5-HT. In contrast, 5-HT failed to rescue reduced expression of Pet1 in 5-Ht1a -/- brainstem explant culture. Conclusions These results suggest a causal relationship between 5-HT1A and Pet1, and reveal a potential mechanism by which 5-HT1A-Pet1 autoregulatory loop is maintained by 5-HT in a spatiotemporal-specific manner during postnatal development. Our results are relevant to understanding the pathophysiology of certain psychiatric and developmental disorders.
[Determination of 5-hydroxytryptamine in plasma by nanofiber solid phase extraction-high performance liquid chromatography].
A novel packed-nanofiber solid phase extraction coupled with high performance liquid chromatography-electrochemical detection (HPLC-ECD) method was established for the determination of 5-hydroxytryptamine (5-HT) in plasma. A 10% (v/v) HClO4 solution was used to precipitate the protein in plasma samples. After homogenizing for 1 min and centrifuging for 10 min at 12 000 r/min, the supernatant was adjusted to pH 8.5 with 0.1 mol/L sodium tetraphenylborate and then derivatized with o-phthalaldehyde (OPA) solution at 30 degrees C for 4 min. The solution was then purified and preconcentrated by the packed-nanofiber solid phase extraction column, in which methanol was used as the eluent. The analyte was analyzed by HPLC-ECD. The chromatographic separation was achieved on a Shimadzu C18 column with pH 5. 4 0. 05 mol/L phosphate buffer solution (containing 0.25 mmol/L ethylene diamine tetraacetic acid)-methanol (60:40, v/v) as mobile phase. The linear range was 5 -500 microg/L with the correlation coefficient (r2) of 0.9996. The limit of detection (S/N = 3) was 1 microg/L. And the spiked recoveries were in the range of 95.6% - 101.4% with the relative standard deviations (RSDs) of intra-day and inter-day assays below 5% (n = 3). On the basis of the advantages of simplicity, high sensitivity and good reproducibility, this method can be used for the determination of 5-HT in human plasma. PMID:22393700
Zhou, Xiaoling; Wang, Yu; Chen, Liqin; Kang, Xuejun
Preclinical and clinical characterization of the selective 5-HT1A receptor antagonist DU-125530 for antidepressant treatment
BACKGROUND AND PURPOSE The antidepressant efficacy of selective 5-HT reuptake inhibitors (SSRI) and other 5-HT-enhancing drugs is compromised by a negative feedback mechanism involving 5-HT1A autoreceptor activation by the excess 5-HT produced by these drugs in the somatodendritic region of 5-HT neurones. 5-HT1A receptor antagonists augment antidepressant-like effects in rodents by preventing this negative feedback, and the mixed ?-adrenoceptor/5-HT1A receptor antagonist pindolol improves clinical antidepressant effects by preferentially interacting with 5-HT1A autoreceptors. However, it is unclear whether 5-HT1A receptor antagonists not discriminating between pre- and post-synaptic 5-HT1A receptors would be clinically effective. EXPERIMENTAL APPROACH We characterized the pharmacological properties of the 5-HT1A receptor antagonist DU-125530 using receptor autoradiography, intracerebral microdialysis and electrophysiological recordings. Its capacity to accelerate/enhance the clinical effects of fluoxetine was assessed in a double-blind, randomized, 6 week placebo-controlled trial in 50 patients with major depression (clinicaltrials.gov identifier NCT01119430). KEY RESULTS DU-125530 showed equal (low nM) potency to displace agonist and antagonist binding to pre- and post-synaptic 5-HT1A receptors in rat and human brain. It antagonized suppression of 5-hydroxytryptaminergic activity evoked by 8-OH-DPAT and SSRIs in vivo. DU-125530 augmented SSRI-induced increases in extracellular 5-HT as effectively as in mice lacking 5-HT1A receptors, indicating a silent, maximal occupancy of pre-synaptic 5-HT1A receptors at the dose used. However, DU-125530 addition to fluoxetine did not accelerate nor augment its antidepressant effects. CONCLUSIONS AND IMPLICATIONS DU-125530 is an excellent pre- and post-synaptic 5-HT1A receptor antagonist. However, blockade of post-synaptic 5- HT1A receptors by DU-125530 cancels benefits obtained by enhancing pre-synaptic 5-hydroxytryptaminergic function.
Scorza, MC; Llado-Pelfort, L; Oller, S; Cortes, R; Puigdemont, D; Portella, MJ; Perez-Egea, R; Alvarez, E; Celada, P; Perez, V; Artigas, F
5-HT1A agonist alleviates serotonergic potentiation of extrapyramidal disorders via postsynaptic mechanisms.
We previously demonstrated that 5-HT stimulants, including selective serotonin reuptake inhibitors (SSRIs), potentiated antipsychotic-induced extrapyramidal symptoms (EPS) by stimulating 5-HT2A/2C, 5-HT3 and 5-HT6 receptors. Here, we studied the effects of the 5-HT1A agonist (▒)-8-hydroxy-2-(di-n-propylamino) tetralin ((▒)-8-OH-DPAT) on the fluoxetine enhancement of EPS (i.e., bradykinesia and catalepsy) to determine if the 5-HT1A agonist can counteract the serotonergic potentiation of EPS. Fluoxetine did not induce EPS signs by itself, but significantly potentiated haloperidol-induced bradykinesia in mice. (▒)-8-OH-DPAT (0.1-1mg/kg, i.p.) significantly attenuated the fluoxetine enhancement of haloperidol-induced bradykinesia in a dose-dependent manner. A selective 5-HT1A antagonist (s)-WAY-100135 completely reversed the anti-EPS action of (▒)-8-OH-DPAT. Microinjection studies using rats revealed that local application of (▒)-8-OH-DPAT into the dorsolateral striatum or the motor cortex significantly diminished fluoxetine-enhanced catalepsy. In contrast, (▒)-8-OH-DPAT injected into the medial raphe nucleus failed to affect EPS induction. The present results illustrate that 5-HT1A agonist can alleviate the SSRI enhancement of EPS by activating postsynaptic 5-HT1A receptors in the striatum and cerebral cortex. PMID:23838274
Shimizu, Saki; Mizuguchi, Yuto; Tatara, Ayaka; Kizu, Tomoya; Andatsu, Saki; Sobue, Akira; Fujiwara, Mai; Morimoto, Tomoki; Ohno, Yukihiro
Molecular properties important for inhaled anesthetic action on human 5-HT3A receptors.
Although inhaled anesthetics have diverse effects on 5-hydroxytryptamine type 3 (5-HT3A) receptors, the mechanism accounting for this diversity is not understood. Studies have shown that modulation of 5-HT3A receptor currents by n-alcohols depends on molecular volume, suggesting that steric interactions between n-alcohols and their binding sites define their action on this receptor. Electrostatic interactions also play an important role in anesthetic action on other ligand-gated receptors. We aimed to determine the contribution of molecular volume and electrostatics in defining volatile anesthetic actions on 5-HT3A receptors. Human 5-HT3A receptors were expressed in, and recorded from, Xenopus oocytes using the two-electrode voltage-clamp technique. The effects of a range of volatile anesthetics, n-alcohols, and nonhalogenated alkanes on submaximal serotonin-evoked peak currents, and full serotonin concentration-response curves were defined. Volatile anesthetics and n-alcohols, but not alkanes, smaller than 0.120 nm3 enhanced submaximal serotonin-evoked peak currents whereas all larger agents reduced currents. Most compounds tested inhibited maximal serotonin-evoked peak currents to varying degrees. However, only agents smaller than 0.120 nm3 shifted the 5-HT3A receptor's serotonin concentration-response curve to the left, whereas larger anesthetics shifted them to the right. Modulation of human 5-HT3A-mediated currents by volatile anesthetics exhibits a dependence on molecular volume consistent with the n-alcohols, suggesting that both classes of agents may enhance 5-HT3A receptor function via the same mechanism. Furthermore, the enhancing but not inhibiting effects of anesthetic compounds on 5-HT3A receptor currents are modulated by electrostatic interactions. PMID:15920198
Stevens, Renna J N; R³sch, Dirk; Davies, Paul A; Raines, Douglas E
The role of serotonin 5-HT7 receptor in regulating sleep and wakefulness.
Abstract Different approaches have been followed to characterize the role of 5-hydroxytryptamine (serotonin) receptor 7 (5-HT7) in the regulation of sleep-wake behavior: (1) 5-HT7 receptor knockout mice spend less time in rapid eye movement sleep than their wild-type counterparts, mainly during the light period. In contrast, there is no difference between the genotypes in time spent in wakefulness or slow-wave sleep. (2) Systemic administration of the selective 5-HT7 receptor agonist LP-211 significantly increased wakefulness (time spent awake) and reduced rapid eye movement sleep in the rat. Direct infusion of LP-211 into the dorsal raphe nucleus, locus coeruleus nucleus, basal forebrain (horizontal limb of the diagonal band of Broca), or laterodorsal tegmental nucleus also produced a decrease in rapid eye movement sleep. Additionally, microinjection of the 5-HT7 receptor agonist into the basal forebrain augmented the time animals remained awake. Local injection of the 5-HT7 receptor agonist LP-44 into the dorsal raphe nucleus also suppressed rapid eye movement sleep in the rat. (3) A similar reduction of rapid eye movement sleep has been described following intraperitoneal injection of the selective 5-HT7 receptor antagonists SB-269970 and SB-656104 in the rat and oral administration of the 5-HT7 receptor antagonist NJ-18038683 to rat and man. Local microinjection of SB-269970 into the dorsal raphe nucleus and basal forebrain also induced a decrease in rapid eye movement sleep in the rat. This tends to suggest that the on-off (activation/blockade), two-state ligand-receptor interaction model is not tenable for the 5-HT7 receptor. PMID:24681431
Monti, Jaime M; Jantos, Hķctor
A pharmacological profile of the selective silent 5HT 1A receptor antagonist, WAY100635
WAY-100635 (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide trihydrochloride) is an achiral phenylpiperazine derivative that binds with high affinity and selectivity to the 5-HT1A receptor. WAY-100635 displaced specific binding of the 5-HT1A radioligand, [3H]8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin), to rat hippocampal membranes with a pIC50 of 8.87. This represented a greater than 100-fold selectivity relative to binding at other 5-HT receptor subtypes and major neurotransmitter receptor, reuptake and ion
Elaine A. Forster; Ian A. Cliffe; David J. Bill; Gillian M. Dover; Deborah Jones; Yvonne Reilly; Allan Fletcher
Effect of ?-mangostin through the inhibition of 5-hydroxytryptamine2A receptors in 5-fluoro-?-methyltryptamine-induced head-twitch responses of mice
Intracerebronventricular (i.c.v.) injection of ?-mangostin (10¢40?nmol/mouse), a major compound of the fruit hull of Garcinia mangostana Lin., like ketanserin (10, 20?nmol/mouse, i.c.v.) inhibited 5-fluoro-?-methyltryptamine (5-FMT) (45?mg?kg?1, i.p.)-induced head-twitch response in mice in the presence or absence of citalopram (a 5-hydroxytryptamine (5-HT)-uptake inhibitor).Neither the 5-FMT- nor the 8-hydroxy-2-(di-n-propylamino)tetralin (5-HT1A-agonist)-induced 5-HT syndrome (head weaving and hindlimb abduction) was affected by ?-mangostin or ketanserin.The locomotor activity stimulated by 5-FMT through the activation of ?1-adrenoceptors did not alter in the presence of ?-mangostin.5-HT-induced inositol phosphates accumulation in mouse brain slices was abolished by ketanserin. ?-Mangostin caused a concentration-dependent inhibition of the inositol phosphates accumulation.?-Mangostin caused a concentration-dependent inhibition of the binding of [3H]-spiperone, a specific 5-HT2A receptor antagonist, to mouse brain membranes.Kinetic analysis of the [3H]-spiperone binding revealed that ?-mangostin increased the Kd value without affecting the Bmax value, indicating the mode of the competitive nature of the inhibition by ?-mangostin.These results suggest that ?-mangostin inhibits 5-FMT-induced head-twitch response in mice by blocking 5-HT2A receptors not by blocking the release of 5-HT from the central neurone. ?-Mangostin is a promising 5-HT2A receptor antagonist in the central nervous system.
Chairungsrilerd, Nattaya; Furukawa, Ken-Ichi; Tadano, Takeshi; Kisara, Kensuke; Ohizumi, Yasushi
Physical Interaction of Calmodulin with the 5-Hydroxytryptamine2C Receptor C-Terminus Is Essential for G Protein-independent, Arrestin-dependent Receptor Signaling
The serotonin (5-hydroxytryptamine; 5-HT)2C receptor is a G protein-coupled receptor (GPCR) exclusively expressed in CNS that has been implicated in numerous brain disorders, including anxio-depressive states. Like many GPCRs, 5-HT2C receptors physically interact with a variety of intracellular proteins in addition to G proteins. Here, we show that calmodulin (CaM) binds to a prototypic Ca2+-dependent ō1-10ö CaM-binding motif located in the proximal region of the 5-HT2C receptor C-terminus upon receptor activation by 5-HT. Mutation of this motif inhibited both ?-arrestin recruitment by 5-HT2C receptor and receptor-operated extracellular signal-regulated kinase (ERK) 1,2 signaling in human embryonic kidney-293 cells, which was independent of G proteins and dependent on ?-arrestins. A similar inhibition was observed in cells expressing a dominant-negative CaM or depleted of CaM by RNA interference. Expression of the CaM mutant also prevented receptor-mediated ERK1,2 phosphorylation in cultured cortical neurons and choroid plexus epithelial cells that endogenously express 5-HT2C receptors. Collectively, these findings demonstrate that physical interaction of CaM with recombinant and native 5-HT2C receptors is critical for G protein-independent, arrestin-dependent receptor signaling. This signaling pathway might be involved in neurogenesis induced by chronic treatment with 5-HT2C receptor agonists and their antidepressant-like activity.
Labasque, Marilyne; Reiter, Eric; Becamel, Carine; Bockaert, Joel
( sup 3 H)-DOB(4-bromo-2,5-dimethoxyphenylisopropylamine) and ( sup 3 H) ketanserin label two affinity states of the cloned human 5-hydroxytryptamine2 receptor
The binding properties of the 5-hydroxytryptamine2 (5-HT2) receptor have been the subject of much interest and debate in recent years. The hallucinogenic amphetamine derivative 4-bromo-2,5-dimethoxyphenylisopropylamine (DOB) has been shown to bind to a small number of binding sites with properties very similar to (3H)ketanserin-labeled 5-HT2 receptors, but with much higher agonist affinities. Some researchers have interpreted this as evidence for the existence of a new subtype of 5-HT2 receptor (termed 5-HT2A), whereas others have interpreted these data as indicative of agonist high affinity and agonist low affinity states for the 5-HT2 receptor. In this investigation, a cDNA clone encoding the serotonin 5-HT2 receptor was transiently transfected into monkey kidney Cos-7 cells and stably transfected into mouse fibroblast L-M(TK-) cells. In both systems, expression of this single serotonin receptor cDNA led to the appearance of both (3H)DOB and (3H)ketanserin binding sites with properties that matched their binding characteristics in mammalian brain homogenates. Addition of guanosine 5'-(beta, gamma-imido) triphosphate (Gpp(NH)p) to this system caused a rightward shift and steepening of agonist competition curves for (3H) ketanserin binding, converting a two-site binding curve to a single low affinity binding state. Gpp(NH)p addition also caused a 50% decrease in the number of high affinity (3H)DOB binding sites, with no change in the dissociation constant of the remaining high affinity states. These data on a single human 5-HT2 receptor cDNA expressed in two different transfection host cells indicate that (3H)DOB and (3H)ketanserin binding reside on the same gene product, apparently interacting with agonist and antagonist conformations of a single human 5-HT2 receptor protein.
Branchek, T.; Adham, N.; Macchi, M.; Kao, H.T.; Hartig, P.R. (Neurogenetic Corporation, Paramus, NJ (USA))
Present and future of 5-HT receptor agonists as antimigraine drugs.
Serotonin (5-hydroxytryptamine; 5-HT) is thought to play an important role in the pathogenesis of migraine. The discovery of the 5-HT1B/1D/1F agonist sumatriptan constitutes a substantial advance in the acute treatment of migraine, though it displays a number of nonnegligible shortcomings. Today, a number of second-generation drugs derived from tryptamine are under advanced clinical development or are about to be marketed worldwide for the acute treatment of migraine. These tryptamine derivatives display partial agonist properties at 5-HT1B/1D receptors. It is not yet clearly established whether these agents represent a major improvement over sumatriptan in therapeutic effectiveness. Most of them also show affinity for 5-ht1F binding sites and have better oral pharmacokinetics than sumatriptan. The acute antimigraine effects of this second-generation of triptans seem to be obtained in largely the same way as with sumatriptan: by cranial vasoconstriction and inhibition of trigeminovascular activation from both peripheral and central projections. Future directions in migraine therapy should focus on agents that exhibit high intrinsic activity at 5-HT1B/1D receptors, offer a good safety profile, and demonstrate long-lasting action which might also be considered in migraine prophylaxis. PMID:10367177
Pauwels, P J; John, G W
Enhancement of cyclic AMP accumulation mediated by 5-HT after chronic amitriptyline treatment in NG 108-15 cells.
1. The effects of chronic in vitro administration of amitriptyline, a tricyclic antidepressant, on 5-hydroxytryptamine (5-HT) receptor-mediated adenylyl cyclase activity was studied in the neuroblastoma x glioma hybrid cell line, NG 108-15. 2. Treatment of NG 108-15 cells with 8 microM amitriptyline for 3 days increased forskolin-stimulated (0.1 microM) adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation. Addition of 5-HT (0.1-100 microM) increased forskolin-stimulated cyclic AMP accumulation in amitriptyline-treated cells in a concentration-dependent manner. However, 5-HT did not affect forskolin-stimulated cyclic AMP accumulation in untreated cells. 3. The 5-HT4 receptor agonist, 5-methoxytryptamine, significantly enhanced forskolin-stimulated cyclic AMP accumulation in amitriptyline-treated cells. In contrast, amitriptyline treatment failed to modify 8-hydroxy-2-(di-n-propylamine) tetralin-induced inhibition of forskolin-stimulated cyclic AMP accumulation. 4. Pretreatment of cells with pertussis toxin did not affect the 5-HT-induced enhancement of cyclic AMP accumulation. 5. The 5-HT-induced enhancement of cyclic AMP accumulation in amitriptyline-treated cells was attenuated by the 5-HT4 receptor antagonists, GR 113808 and ICS 205-930, with relatively low potency. However, spiperone, SCH 23390, and pindolol were completely ineffective against this 5-HT-induced enhancement. 6. Chronic treatment with amitriptyline did not modify the cyclic AMP production stimulated by prostaglandin E1 or cholera toxin. This treatment also had no effect on GTP gamma S-, NaF-, and Mn(2+)-stimulated cyclic AMP accumulation in isolated cell membranes. 7. Chronic treatment with the 5-HT receptor antagonists, pindolol or ICS 205-930, did not inhibit the 5-HT-induced enhancement of cyclic AMP accumulation.8. Chronic treatment with other antidepressant drugs, imipramine, mianserin or paroxetine, elicited the 5-HT-induced enhancement of cyclic AMP accumulation.9. Taken together, these results suggest that chronic amitriptyline treatment of NG 108-15 cells causes 5-HT to enhance forskolin-stimulated cyclic AMP accumulation by enhancing 5-HT receptor-mediated stimulation of adenylyl cyclase and not by reducing 5-HT-mediated inhibition of adenylyl cyclase. The 5-HT-induced enhancement of cyclic AMP accumulation in amitriptyline-treated cells may result from changes at the level of the 5-HT receptor rather than at the level of G, proteins or adenylyl cyclase. It is unlikely that this enhancement of cyclic AMP accumulation is caused by long-term antagonism of the 5-HT receptor by amitriptyline. PMID:7620719
Shimizu, M; Nishida, A; Fukuda, H; Saito, H; Yamawaki, S
The aggression and behavioral abnormalities associated with monoamine oxidase A deficiency are rescued by acute inhibition of serotonin reuptake.
The termination of serotonin (5-hydroxytryptamine, 5-HT) neurotransmission is regulated by its uptake by the 5-HT transporter (5-HTT), as well as its degradation by monoamine oxidase (MAO)-A. MAO-A deficiency results in a wide set of behavioral alterations, including perseverative behaviors and social deficits. These anomalies are likely related to 5-HTergic homeostatic imbalances; however, the role of 5-HTT in these abnormalities remains unclear. To ascertain the role of 5-HTT in the behavioral anomalies associated to MAO-A deficiency, we tested the behavioral effects of its blocker fluoxetine on perseverative, social and aggressive behaviors in transgenic animals with hypomorphic or null-allele MAO-A mutations. Acute treatment with the 5-HTT blocker fluoxetine (10Āmg/kg, i.p.) reduced aggressive behavior in MAO-A knockout (KO) mice and social deficits in hypomorphic MAO-A(Neo) mice. Furthermore, this treatment also reduced perseverative responses (including marble burying and water mist-induced grooming) in both MAO-A mutant genotypes. Both MAO-A mutant lines displayed significant reductions in 5-HTT expression across the prefrontal cortex, amygdala and striatum, as quantified by immunohistochemical detection; however, the down-regulation of 5-HTT in MAO-A(Neo) mice was more pervasive and widespread than in their KO counterparts, possibly indicating a greater ability of the hypomorphic line to enact compensatory mechanisms with respect to 5-HT homeostasis. Collectively, these findings suggest that the behavioral deficits associated with low MAO-A activity may reflect developmental alterations of 5-HTT within 5-HTergic neurons. Furthermore, the translational implications of our results highlight 5-HT reuptake inhibition as an interesting approach for the control of aggressive outbursts in MAO-A deficient individuals. PMID:24882701
Godar, Sean C; Bortolato, Marco; Castelli, M Paola; Casti, Alberto; Casu, Angelo; Chen, Kevin; Ennas, M Grazia; Tambaro, Simone; Shih, Jean C
Targeted inhibition of serotonin type 7 (5-HT7) receptor function modulates immune responses and reduces the severity of intestinal inflammation.
Mucosal inflammation in conditions ranging from infective acute enteritis or colitis to inflammatory bowel disease is accompanied by alteration in serotonin (5-hydroxytryptamine [5-HT]) content in the gut. Recently, we have identified an important role of 5-HT in the pathogenesis of experimental colitis. 5-HT type 7 (5-HT7) receptor is one of the most recently identified members of the 5-HT receptor family, and dendritic cells express this receptor. In this study, we investigated the effect of blocking 5-HT7 receptor signaling in experimental colitis with a view to develop an improved therapeutic strategy in intestinal inflammatory disorders. Colitis was induced with dextran sulfate sodium (DSS) or dinitrobenzene sulfonic acid (DNBS) in mice treated with selective 5-HT7 receptor antagonist SB-269970, as well as in mice lacking 5-HT7 receptor (5-HT7(-/-)) and irradiated wild-type mice reconstituted with bone marrow cells harvested from 5-HT7(-/-) mice. Inhibition of 5-HT7 receptor signaling with SB-269970 ameliorated both acute and chronic colitis induced by DSS. Treatment with SB-269970 resulted in lower clinical disease, histological damage, and proinflammatory cytokine levels compared with vehicle-treated mice post-DSS. Colitis severity was significantly lower in 5-HT7(-/-) mice and in mice reconstituted with bone marrow cells from 5-HT7(-/-) mice compared with control mice after DSS colitis. 5-HT7(-/-) mice also had significantly reduced DNBS-induced colitis. These observations provide us with novel information on the critical role of the 5-HT7 receptor in immune response and inflammation in the gut, and highlight the potential benefit of targeting this receptor to alleviate the severity of intestinal inflammatory disorders such as inflammatory bowel disease. PMID:23554310
Kim, Janice J; Bridle, Byram W; Ghia, Jean-Eric; Wang, Huaqing; Syed, Shahzad N; Manocha, Marcus M; Rengasamy, Palanivel; Shajib, Mohammad Sharif; Wan, Yonghong; Hedlund, Peter B; Khan, Waliul I
The stimulatory and inhibitory components of cocaine's actions on the 5HTP-induced 5HT 2A receptor response
Previously we have shown that cocaine attenuates the 5-HT2A receptor-mediated head-twitch response (HTR) in mice produced by the 5-HT2A\\/C direct agonist (▒)-1(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). This inhibition appears to be due to cocaine-induced indirect stimulation of the inhibitory serotonergic 5-HT1A and noradrenergic ?2 receptors via the inhibition of reuptake of synaptic serotonin (5-HT) and norepinephrine (NE), respectively. In the present study, we
Nissar A. Darmani; Sharon L. Reeves
Inhibition of 5-hydroxytryptamine and noradrenaline uptake in platelets and synaptosomes incubated in plasma from human subjects treated with amitriptyline or nortriptyline: Utilization of the principle for a bioassay method
To estimate the inhibition of amine uptake caused in vivo by tricyclic drugs used at a clinical dose, normal human blood platelets or rat hypothalamic or cortical synaptosomes were incubated with 3H-5-hydroxytryptamine (3H-5-HT) or 3H-noradrenaline (3H-NA) in platelet-free plasma of healthy volunteers receiving a single dose of 50 mg amitriptyline (AT) or nortriptyline (NT) orally. Venous blood samples were taken
Jouko Tuomisto; Erkki Tukiainen; Raija Voutilainen; Põivi Tuomainen
High-frequency HTR3B variant associated with major depression dramatically augments the signaling of the human 5-HT3AB receptor
The 5-hydroxytryptamine-3 (5-HT3) receptor mediates the fast excitatory neurotransmission of serotonin and is known to mediate the nausea/emesis induced by radio/chemotherapy and anesthetics. A polymorphism encoding the variation Y129S in the 5-HT3B subunit exists in high frequency in the general population and has been shown to be inversely correlated to the incidence of major depression in women. We show that 5-HT3AB(Y129S) receptors exhibit a substantially increased maximal response to serotonin compared with WT receptors in two fluorescence-based cellular assays. In electrophysiological recordings, the deactivation and desensitization kinetics of the 5-HT3AB(Y129S) receptor are 20- and 10-fold slower, respectively, than those of the WT receptor. Single-channel measurements reveal a 7-fold-increased mean open time of 5-HT3AB(Y129S) receptors compared with WT receptors. The augmented signaling displayed by 5-HT3AB(Y129S) receptors may confer protection against the development of depression. The variant also may influence the development and/or treatment of nausea and other disorders involving 5-HT3 receptors. Thus, the impact of the high-frequency variant 5-HT3B(Y129S) on 5-HT3AB receptor signaling calls for a search for additional phenotypes, and the variant may thus aid in establishing the role of the 5-HT3AB receptor in pathophysiology.
Krzywkowski, Karen; Davies, Paul A.; Feinberg-Zadek, Paula L.; Brauner-Osborne, Hans; Jensen, Anders A.
Expression of 5-HT1A receptor mRNA in rat dorsal raphe nucleus and ventrolateral periaqueductal gray neurons after peripheral inflammation.
In the present study we observed the expression of 5-hydroxytryptamine (5-HT)1A receptor mRNA in the dorsal raphe nucleus (DRN) and ventrolateral periaqueductal gray (vlPAG) neurons, especially in 5-HT immunoreactive neurons (5-HT-IR), using in situ hybridization (ISH) and double staining with fluorescent ISH (FISH) and immunohistochemical (FIH) techniques. The findings of this study demonstrated that 5-HT1A receptor mRNA was expressed with moderate to high level in the DRN and vlPAG neurons. Following carrageenan inflammation, the expression of 5-HT1A receptor mRNA in the DRN and bilateral vlPAG neurons was significantly increased. The peak occurred at 3-8h followed by a clear decrease at 24 h, which basically corresponded to the time-course of behavioral hyperalgesia. Moderate 5-HT1A receptor mRNA and 5-HT immunoreactive (5-HT-IR) double-labeled cells were observed in the DRN and vlPAG, suggesting that some of 5-HT1A receptors in the DRN and vlPAG may be autoreceptors. Eight hours after carrageenan injection, the number of the double labeled cells was significantly increased. These results suggest that the synthesis of 5-HT1A receptors, including autoreceptors, is increased in the DRN and vlPAG during peripheral inflammation. PMID:11059903
Zhang, Y Q; Gao, X; Huang, Y L; Wu, G C
Towards metabolically stable 5-HT7 receptor ligands: a study on 1-arylpiperazine derivatives and related isosters.
Serotonin 7 (5-hydroxytryptamine7 or 5-HT7) is the most recently identified serotonin receptor. It is involved in mood disorders and is studied as a target for antidepressants. Here, we report on the structural manipulation of the 5-HT7 receptor ligand 4-[2-(3-methoxyphenyl)ethyl]-1-(2-methoxyphenyl)piperazine (1a) aimed at obtaining 5-HT7 receptor ligands endowed with good in vitro metabolic stability. A set of N-[3-methoxyphenyl)ethyl-substituted] 1-arylpiperazine, 4-arylpiperidine and 1-aryl-4-aminopiperidine was synthesized and tested in radioligand binding assays at human cloned 5-HT7 and 5-HT1A receptors. In vitro metabolic stability of the target compounds was assessed after incubation with rat hepatic S9 microsomal fraction. Among the new compounds, 1-(2-biphenyl)-4-[2-(3-methoxyphenyl)ethyl]piperazine (1d) and 4-(2-biphenyl)-1-[2-(3-methoxyphenyl)ethyl]piperidine (2d) showed a good compromise between affinity at 5-HT7 receptor (K iĀ=Ā7.5 nM and 13 nM, respectively) and in vitro metabolic stability (26 and 65Ā% recovery of parent compound, respectively) but were poorly selective over 5-HT1A receptor. PMID:23571499
Lacivita, Enza; De Giorgio, Paola; Patarnello, Daniela; Niso, Mauro; Colabufo, Nicola A; Berardi, Francesco; Perrone, Roberto; Satala, Grzegorz; Duszynska, Beata; Bojarski, Andrzej J; Leopoldo, Marcello
An electrophysiological investigation of the properties of 5-HT3 receptors of rabbit nodose ganglion neurones in culture.
1. The biophysical and pharmacological properties of 5-hydroxytryptamine (5-HT)-evoked currents in rabbit nodose ganglion neurones in culture have been determined by use of the whole-cell and outside-out membrane patch recording modes of the patch-clamp technique. 2. In 49% of cells investigated the bath application of 10(-5) M 5-HT at negative holding potentials elicited an inward current. The whole-cell response to 5-HT reversed in sign (E5-HT) at approximately -2 mV and exhibited inward rectification. 3. The influence of various ion substitutions upon E5-HT established that the 5-HT-evoked current is mainly mediated by a mixed Na+, K+ cation conductance with little or no contribution from Cl- ions. The omission of Ca2+ and Mg2+ from the extracellular solution enhanced the amplitude of the 5-HT-induced current. 4. On isolated outside-out membrane patches, the bath application of 10(-6) M 5-HT induced single channel currents with a chord conductance of approximately 17 pS at -70 mV and an average slope conductance of 19 pS over the range -100 to -40 mV. The 5-HT-induced single channels exhibited modest inward rectification and were reduced in frequency, but not amplitude, by the 5-HT3 receptor antagonist metoclopramide (10(-6) M). 5. The bath application of 5-HT (3 x 10(-7)-3 x 10(-5) M) to whole cells voltage clamped at -60 mV produced dose-dependent inward currents which were mimicked by 2-methyl-5-HT and 1-phenylbiguanide with equipotent molar ratios, relative to 5-HT, of 2.5 and 32 respectively. 6. Whole-cell inward currents produced by the local pressure application of 5-HT (10(-5) M) were unaffected by 10(-6) M methysergide, 10(-6) M ketanserin or 10(-6) M citalopram, but were concentration-dependently antagonized by the selective 5-HT3 receptor antagonists tropisetron (IC50 = 4.6 x 10(-11) M) ondansetron (IC50 = 5.7 x 10(-11) M), and bemesetron (IC50 = 3.3 x 10(-10) M). The response to 5-HT was also blocked by the non-selective antagonists metoclopramide (IC50 = 1.2 x 10(-8) M), cocaine (IC50 = 8.3 x 10(-8) M) and (+)-tubocurarine (IC50 = 1.6 x 10(-7) M).
Peters, J. A.; Malone, H. M.; Lambert, J. J.
Evidence for postsynaptic mediation of the hypothermic effect of 5-HT1A receptor activation.
1. The 5-HT1A ligand BMY 7378 (8-[2[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]8-azaspirol [4,5]-decane-7,9-dione dihydrochloride, 0.032-2 mg kg-1, s.c.) caused hyperphagia, a response to the activation of presynaptic 5-HT1A receptors. 2. BMY 7378 (8 mg kg-1, s.c.) and the 5-HT1A agonist (8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), 0.10 and 0.25 mg kg-1 s.c.) also caused hypothermia. This was inhibited by (-)-pindolol (1-mg kg-1, i.p.) and not prevented by pretreatments with p-chlorophenylalanine which grossly depleted 5-hydroxytryptamine (5-HT) from terminal regions. The hypothermic effects are explicable by activation of postsynaptic 5-HT1A receptors. Infusion of BMY 7378 (8-64 micrograms) into the dorsal raphe was without convincing hypothermic effect. 3. BMY 7378 (8 mg kg-1, s.c.) inhibited another effect of activation of postsynaptic 5-HT1A receptors, i.e., the induction of components of the 5-HT syndrome by 8-OH-DPAT (0.5, 1.0 mg kg-1, s.c.) which suggests that BMY 7378 has antagonistic as well as agonistic effects at these sites. 4. Partial agonist properties of BMY 7378 at postsynaptic sites were also indicated by doses for hypothermia being much greater than those for hyperphagia i.e., ED50 (hypothermia) greater than 2 mg kg-1, ED50 (hyperphagia) = 0.010 mg kg-1. This contrasts with the similar ED50 values for both the hypothermic (ED50 = 0.08-0.10 mg kg-1) and hyperphagic (ED50 = 0.06-0.10 mg kg-1) effects of 8-OH-DPAT.(ABSTRACT TRUNCATED AT 250 WORDS)
O'Connell, M. T.; Sarna, G. S.; Curzon, G.
Peptide Inhibitors Disrupt the Serotonin 5-HT2C Receptor Interaction with Phosphatase and Tensin Homolog to Allosterically Modulate Cellular Signaling and Behavior
Serotonin (5-hydroxytryptamine; 5-HT) signaling through the 5-HT2C receptor (5-HT2CR) is essential in normal physiology, whereas aberrant 5-HT2CR function is thought to contribute to the pathogenesis of multiple neural disorders. The 5-HT2CR interacts with specific protein partners, but the impact of such interactions on 5-HT2CR function is poorly understood. Here, we report convergent cellular and behavioral data that the interaction between the 5-HT2CR and protein phosphatase and tensin homolog (PTEN) serves as a regulatory mechanism to control 5-HT2CR-mediated biology but not that of the closely homologous 5-HT2AR. A peptide derived from the third intracellular loop of the human 5-HT2CR [3L4F (third loop, fourth fragment)] disrupted the association, allosterically augmented 5-HT2CR-mediated signaling in live cells, and acted as a positive allosteric modulator in rats in vivo. We identified the critical residues within an 8 aa fragment of the 3L4F peptide that maintained efficacy (within the picomolar range) in live cells similar to that of the 3L4F peptide. Last, molecular modeling identified key structural features and potential interaction sites of the active 3L4F peptides against PTEN. These compelling data demonstrate the specificity and importance of this protein assembly in cellular events and behaviors mediated by 5-HT2CR signaling and provide a chemical guidepost to the future development of drug-like peptide or small-molecule inhibitors as neuroprobes to study 5-HT2CR allostery and therapeutics for 5-HT2CR-mediated disorders.
Anastasio, Noelle C.; Gilbertson, Scott R.; Bubar, Marcy J.; Agarkov, Anton; Stutz, Sonja J.; Jeng, Yowjiun; Bremer, Nicole M.; Smith, Thressa D.; Fox, Robert G.; Swinford, Sarah E.; Seitz, Patricia K.; Charendoff, Marc N.; Craft, John W.; Laezza, Fernanda M.; Watson, Cheryl S.; Briggs, James M.; Cunningham, Kathryn A.
Binding modes of chain arylpiperazines to 5-HT1a, 5-HT2a and 5-HT7 receptors.
An overview of docking models of chain arylpiperazines to different subtypes of serotonin receptors belonging to the GPCR family is presented. The theory of a ligand-receptor interaction has been briefly summarized. The review covers more than twenty models, beginning with the early models of a ligand interaction with the 5-HT1A and 5-HT2A receptor, and ending with a ligand-5-HT7 receptor docking studies. PMID:24568298
Bielenica, Anna; Kozio?, Anna E; Struga, Marta
Small molecule drug screening in Drosophila identifies the 5HT2A receptor as a feeding modulation target
Dysregulation of eating behavior can lead to obesity, which affects 10% of the adult population worldwide and accounts for nearly 3 million deaths every year. Despite this burden on society, we currently lack effective pharmacological treatment options to regulate appetite. We used Drosophila melanogaster larvae to develop a high-throughput whole organism screen for drugs that modulate food intake. In a screen of 3630 small molecules, we identified the serotonin (5-hydroxytryptamine or 5-HT) receptor antagonist metitepine as a potent anorectic drug. Using cell-based assays we show that metitepine is an antagonist of all five Drosophila 5-HT receptors. We screened fly mutants for each of these receptors and found that serotonin receptor 5-HT2A is the sole molecular target for feeding inhibition by metitepine. These results highlight the conservation of molecular mechanisms controlling appetite and provide a method for unbiased whole-organism drug screens to identify novel drugs and molecular pathways modulating food intake.
Gasque, Gabriel; Conway, Stephen; Huang, Juan; Rao, Yi; Vosshall, Leslie B.
Differential inverse agonist efficacies of SB258719, SB258741 and SB269970 at human recombinant serotonin 5HT 7 receptors
Recombinant 5-hydroxytryptamine 5-HT7 receptors are known to express constitutive, i.e., agonist-independent activity. Nonselective ligands, like methiothepin, ritanserin or clozapine behave as full inverse agonists at 5-HT7 receptors. The aim of the present study was to evaluate the degree of inverse agonist activity of three selective 5-HT7 receptor antagonists ((R)-3,N-dimethyl-N-[1-methyl-3-(4-methyl-piperidin-1-yl)propyl]benzene sulfonamide or SB-258719, R-(+)-1-(toluene-3-sulfonyl)-2-[2-(4-methylpiperidin-1-yl)ethyl]-pyrrolidine or SB-258741 and (R)-3-(2-(2-(4-methylpiperidin-1-yl)ethyl)-pyrrolidine-1-sulfonyl)-phenol or SB-269970) in
Cķcile Mahķ; Erika Loetscher; Dominik Feuerbach; Werner M³ller; Max P Seiler; Philippe Schoeffter
Characterization of serotonin 5-hydroxytryptamine-1A receptor activation using a phospho-extracellular-signal regulated kinase 2 sensor.
The activation of G-protein-coupled receptors (GPCRs) can result in the stimulation of numerous signaling networks that extend beyond canonical secondary messenger-dependent pathways. It is well-established that many of these diverse networks converge on the MAPK pathway, resulting in the activation of extracellular-signal regulated kinase 1/2 (ERK). Since the link between GPCRs and ERK can be modulated via both G-protein-dependent and -independent mechanisms, measurement of ERK phosphorylation may serve as an ideal surrogate for GPCR activation. We have combined BacMam-mediated gene delivery of the GFP-ERK2 with a time-resolved Foerster resonance energy transfer (TR-FRET) immunoassay for the measurement of intracellular phospho-ERK2 levels. Together these technologies enable a flexible platform for measuring GPCR and MAPK activation in the cell line of interest. This technology has been applied to the measurement of activation of the serotonin 5-hydroxytryptamine-1A (5-HT(1A)) receptor expressed in CHO-K1 cells. In addition to demonstrating the flexibility of this assay platform, we provide the first reported profile for 5-HT(1A) receptor-mediated ERK activation using a panel of known Parkinson's disease drugs. Our results demonstrate the value of using ERK activation as a downstream sensor for GPCR function, providing an attractive complement to upstream endpoints such as ligand occupancy and binding of GTPgammaS. PMID:19539597
Huwiler, Kristin G; Machleidt, Thomas; Chase, Lucas; Hanson, Bonnie; Robers, Matthew B
Studies on the relative effects of prostaglandins, bradykinin, 5-hydroxytryptamine and histamine on the synovial microcirculation in dogs.
1 The relative effects of prostaglandins E1, E2, F1alpha, F2alpha, bradykinin, histamine and 5-hydroxytryptamine (5-HT) on the canine synovial microcirculation were investigated using the rate of clearance of radioactive xenon (133Xe) as an index of synovial perfusion. 2 All the compounds tested, except prostaglandin F1alpha, produced a vasodilator effect. The descending order of potency of the active compounds was (i) prostaglandin E1, (ii) prostaglandin E2 and bradykinin, (iii) histamine and 5-HT, (iv) prostaglandin F2alpha. The most potent compound tested, prostaglandin E1 produced an effect in nanogram amounts in each joint. 3 Prostaglandin F2alpha has been reported to have an anti-inflammatory action; however no evidence was found of antagonism of prostaglandin E1 by two dose levels of prostaglandin F2alpha. 4 Preliminary studies showed that threshold doses of prostaglandin E1 did not potentiate the vasodilator action of threshold or sub-threshold doses of bradykinin in the dog synovium.
Dick, W C; Grennan, D M; Zeitlin, I J
Sevoflurane induced amnesia inhibits hippocampal Arc expression partially through 5-hydroxytryptamine-7 receptors in the bilateral basolateral amygdala in rats.
This study aimed to investigate whether the regulation of 5-hydroxytryptamine-7 (5-HT7) receptors in the bilateral basolateral amygdala (BLA) could alter the amnesic effects of sevoflurane and change the hippocampal expression of Arc and neural apoptosis. Male Sprague-Dawley rats were randomized into ten groups. First, the animals received bilateral injection of SB269970 (20, 50, or 100 pmol/0.2 ?l) or saline (0.2 ?l) or AS-19 (2, 10, or 50 pmol/0.2 ?l), followed by inhalation of 2% sevoflurane or air for 2h. Then, fear conditioning training was carried out, and the percentage of freezing was detected 24h later. Furthermore, hippocampal Arc protein level and neural apoptosis were measured. Pre-training inhalation of sevoflurane reduced the extent of freezing, and hippocampal Arc expression. The largest dose of SB269970 (100 pmol) could block sevoflurane-induced amnesia and reverse the inhibitive effect of sevoflurane on Arc expression, while the maximal dose of AS-19 could exacerbate the amnesic effect, and further inhibit Arc expression. Furthermore, pre-training inhalation of 2% sevoflurane for 6h could not induce neural apoptosis in the hippocampus. The amnesic effect of sevoflurane might partly attribute to its impairment of memory formation in the hippocampus via activation of 5-HT7 receptors in the BLA. PMID:24406149
Zhang, Fujun; Feng, Xiaomei; Zeng, Qingwen; Wang, Bo; Wilhelmsen, Kevin; Li, Qiang; Cao, Xiaohua; Yu, Buwei
An in vivo dialysis and behavioural study of the release of 5-HT by p-chloroamphetamine in reserpine-treated rats.
1. Reserpine (2.5 mg kg-1 i.p.) decreased rat brain 5-hydroxytryptamine (5-HT) by 86% 24 h later but most components of the 5-HT-dependent behavioural syndrome induced by p-chloroamphetamine (PCA, 5 mg kg-1 i.p.) or 5-methoxy-N,N-dimethyltryptamine (5-MeODMT, 5 mg kg-1 i.p.) over 1 h after administration were unaffected. However, Straub tail was increased after giving PCA or 5-MeODMT and head weaving was decreased after giving 5-MeODMT. 2. Frontal cortex extracellular 5-HT concentrations of vehicle pretreated rats before injection of PCA, as calculated from dialysate 5-HT concentrations, were about 1/1000th of corresponding brain values. Extracellular 5-hydroxyindoleacetic acid (5-HIAA) and brain values were comparable with each other. Dialysate 5-HT increased after PCA with peak values at 20-40 min. 3. Reserpine pretreatment reduced dialysate 5-HT concentration before PCA was given but the net increase (AUC) over the 1 h after PCA did not differ significantly from that seen in animals pretreated with vehicle. Dialysate 5-HIAA values slowly decreased after PCA injection in both reserpine and vehicle pretreated groups. 4. The results suggest that PCA causes the 5-HT syndrome by releasing 5-HT from the neuronal cytoplasm but that physiological release of 5-HT occurs from vesicular stores.
Adell, A.; Sarna, G. S.; Hutson, P. H.; Curzon, G.
Medicinal chemistry strategies to 5-HT(6) receptor ligands as potential cognitive enhancers and antiobesity agents.
Although the 5-hydroxytryptamine(6) (5-HT(6)) receptor was discovered only recently, its almost exclusive distribution in the brain makes it a promising, novel, target for central nervous system (CNS)-mediated diseases such as Alzheimer's disease (cognitive function), schizophrenia, anxiety and obesity. In the past few years a significant research interest has advanced the understanding of the functional roles and the pharmacophore requirements of this receptor. Two 5-HT(6) receptor antagonists have already entered Phase II clinical trials for the enhancement of cognitive function. Since the first discovery of selective ligands for the 5-HT(6) receptor by HTS in 1998, several medicinal-chemistry-driven approaches have delivered highly selective lead structures with well-defined functionalities, starting from either the endogenous ligand 5-HT or the chemical structures identified by HTS. The concept of 'scaffold hopping' has been employed to expand the variability of the available chemical scaffolds and to generate patentable ligands. Supported by pharmacophore models, which have been established recently, the binding and functionality (structure-activity relationships) of the lead structures have been optimized further. PMID:16580970
Holenz, J÷rg; Pauwels, Petrus J; DĒaz, Josķ Luis; MercĶ, Ramon; Codony, Xavier; Buschmann, Helmut
Role of serotonin in angiogenesis: induction of angiogenesis by sarpogrelate via endothelial 5-HT1B/Akt/eNOS pathway in diabetic mice.
Serotonin (5-hydroxytryptamine, 5-HT) plays a crucial role in peripheral artery disease (PAD) and diabetes mellitus (DM). In these conditions, the balance between the 5-HT2A receptor in smooth muscle cells and the 5-HT1B receptor in endothelial cells (ECs) regulates vascular tonus. In the present study, we focused on the role of 5-HT in endothelial dysfunction using a selective 5-HT2A receptor blocker, sarpogrelate. In human EC, 5-HT markedly stimulated eNOS expression and the phosphorylation of eNOS, Akt and ERK1/2. In addition, a dose-dependent increase in tubule-formation on Matrigel was observed after 5-HT treatment. In contrast, high glucose significantly inhibited tubule formation and eNOS expression through inactivation of Akt, while 5-HT significantly attenuated these actions of high glucose (P<0.01). These results indicate that 5-HT stimulated angiogenesis through activation of Akt in ECs. However, in clinical situations, 5-HT seems to act as the "devil". To examine the role of 5-HT in diabetic PAD, a hindlimb ischemia model was created in diabetic mice. The blood flow ratio of the ischemic to non-ischemic limb was significantly lower in DM mice than in normal mice, while sarpogrelate significantly attenuated the decrease in the blood flow ratio compared to control (P<0.01). Consistently, the decrease in eNOS expression and Akt activity in DM mice was significantly attenuated by sarpogrelate. Overall, the present study demonstrated that selective inhibition of 5-HT2A by sarpogrelate significantly restored ischemic limb blood perfusion in a severe diabetic mouse model through stimulation of the eNOS/Akt pathway via the endothelial 5-HT1B receptor. Enhancement of vasodilation and angiogenesis by sarpogrelate might provide a unique treatment for PAD and DM patients. PMID:22172591
Iwabayashi, Masaaki; Taniyama, Yoshiaki; Sanada, Fumihiro; Azuma, Junya; Iekushi, Kazuma; Kusunoki, Hiroshi; Chatterjee, Amarnath; Okayama, Keita; Rakugi, Hiromi; Morishita, Ryuichi
Simultaneous determination of 5-hydroxyindoleacetic acid and 5-hydroxytryptamine in urine samples from patients with acute appendicitis by liquid chromatography using poly(bromophenol blue) film modified electrode.
The fabrication and application of a novel electrochemical detection (ED) system with a poly(bromophenol blue) (PBPB) film chemically modified electrode (CME) for high performance liquid chromatography (HPLC) were described. The electrochemical behaviors of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) at this CME were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the PBPB CME efficiently exhibited electrocatalytic effect on the current responses of 5-HT and 5-HIAA with relatively high sensitivity, stability and long life of activity. In HPLC-ED, the two analytes had good and stable current responses at the CME and their linear ranges were over four orders of magnitude (R> or =0.9992) with the detection limits being 0.25 nmol L(-1) for 5-HT and 0.50 nmol L(-1) for 5-HIAA. The application of this method for the determination of 5-HT and 5-HIAA in urine samples from patients with acute appendicitis (AA) was satisfactory. PMID:16949889
Xu, Haihong; Zhang, Wen; Wang, Dan; Zhu, Wei; Jin, Litong
A Chemocentric Informatics Approach to Drug Discovery: Identification and Experimental Validation of Selective Estrogen Receptor Modulators as ligands of 5-Hydroxytryptamine-6 Receptors and as Potential Cognition Enhancers
We have devised a chemocentric informatics methodology for drug discovery integrating independent approaches to mining biomolecular databases. As a proof of concept, we have searched for novel putative cognition enhancers. First, we generated Quantitative Structure- Activity Relationship (QSAR) models of compounds binding to 5-hydroxytryptamine-6 receptor (5HT6R), a known target for cognition enhancers, and employed these models for virtual screening to identify putative 5-HT6R actives. Second, we queried chemogenomics data from the Connectivity Map (http://www.broad.mit.edu/cmap/) with the gene expression profile signatures of AlzheimerÆs disease patients to identify compounds putatively linked to the disease. Thirteen common hits were tested in 5-HT6R radioligand binding assays and ten were confirmed as actives. Four of them were known selective estrogen receptor modulators that were never reported as 5-HT6R ligands. Furthermore, nine of the confirmed actives were reported elsewhere to have memory-enhancing effects. The approaches discussed herein can be used broadly to identify novel drug-target-disease associations.
Hajjo, Rima; Setola, Vincent; Roth, Bryan L.; Tropsha, Alexander
Contrasting contribution of 5-hydroxytryptamine 1A receptor activation to neurochemical profile of novel antipsychotics: frontocortical dopamine and hippocampal serotonin release in rat brain.
Several novel antipsychotics, such as aripiprazole, bifeprunox, SSR181507 [(3-exo)-8-benzoyl-N-(((2S)7-chloro-2,3-dihydro-1,4-benzodioxin-1-yl)methyl)-8-azabicyclo(3.2.1)octane-3-methanamine], and SLV313 [1-(2,3-dihydro-benzo[1,4]dioxin-5-yl)-4-[5-(4-fluorophenyl)-pyridin-3-ylmethyl]-piperazine], activate serotonin 5-hydroxytryptamine (5-HT)1A receptors. Such activity is associated with enhanced treatment of negative symptoms and cognitive deficits, which may be mediated by modulation of cerebral dopamine and serotonin levels. We employed microdialysis coupled to high pressure liquid chromatography with electrochemical detection to examine 5-HT1A receptor activation in the modulation of extracellular dopamine in medial prefrontal cortex and serotonin in hippocampus of freely moving rats. The above compounds were compared with drugs that have less interaction with 5-HT1A receptors (clozapine, nemonapride, ziprasidone, olanzapine, risperidone, and haloperidol). Hippocampal 5-HT was decreased by bifeprunox, SSR181507, SLV313, sarizotan, and nemonapride, effects similar to those seen with the 5-HT1A agonist, (+)-8-hydroxy-2-(di-n-propylamino)tetralin [(+)8-OH-DPAT], consistent with activation of 5-HT1A autoreceptors. These decreases were reversed by the selective 5-HT1A antagonist, WAY100635 [N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide]. In contrast, haloperidol, risperidone, clozapine, olanzapine, ziprasidone, and aripiprazole did not significantly modify hippocampal serotonin levels. In medial prefrontal cortex, dopamine levels were increased by SSR181507, SLV313, sarizotan, and (+)8-OH-DPAT. These effects were reversed by WAY100635, indicating mediation by 5-HT1A receptors. In contrast, the increases in dopamine levels induced by clozapine, risperidone, olanzapine, and ziprasidone were not blocked by WAY100635, consistent with predominant influence of other mechanisms in the actions of these drugs. Haloperidol, nemonapride, and the D2 partial agonists, aripiprazole and bifeprunox, did not significantly alter dopamine release. Taken together, these data demonstrate the diverse contribution of 5-HT1A receptor activation to the profile of antipsychotics and suggest that novel drugs selectively targeting D2 and 5-HT1A receptors may present distinctive therapeutic properties. PMID:15987834
Assiķ, Marie-Bernadette; Ravailhe, Vķronique; Faucillon, Valķrie; Newman-Tancredi, Adrian
Selective 5-HT1B receptor inhibition of glutamatergic and GABAergic synaptic activity in the rat dorsal and median raphe
The dorsal (DR) and median (MR) raphe nuclei contain 5-hydroxytryptamine (5-HT) cell bodies that give rise to the majority of the ascending 5-HT projections to the forebrain. The DR and MR have differential roles in mediating stress, anxiety and depression. Glutamate and GABA activity sculpt putative 5-HT neuronal firing and 5-HT release in a seemingly differential manner in the MR and DR, yet isolated glutamate and GABA activity within the DR and MR has not been systematically characterized. Visualized whole-cell voltage-clamp techniques were used to record excitatory and inhibitory postsynaptic currents (EPSC and IPSC) in 5-HT-containing neurons. There was a regional variation in action potential-dependent (spontaneous) and basal [miniature (m)] glutamate and GABAergic activity. mEPSC activity was greater than mIPSC activity in the DR, whereas in the MR the mIPSC activity was greater. These differences in EPSC and IPSC frequency indicate that glutamatergic and GABAergic input have distinct cytoarchitectures in the DR and MR. 5-HT1B receptor activation decreased mEPSC frequency in the DR and the MR, but selectively inhibited mIPSC activity only in the MR. This finding, in concert with its previously described function as an autoreceptor, suggests that 5-HT1B receptors influence the ascending 5-HT system through multiple mechanisms. The disparity in organization and integration of glutamatergic and GABAergic input to DR and MR neurons and their regulation by 5-HT1B receptors may contribute to the distinction in MR and DR regulation of forebrain regions and their differential function in the aetiology and pharmacological treatment of psychiatric disease states.
Lemos, Julia C.; Pan, Yu-Zhen; Ma, Xiaohong; Lamy, Christophe; Akanwa, Adaure C.; Beck, Sheryl G.
RhoBTB3 interacts with the 5-HT7a receptor and inhibits its proteasomal degradation.
The 5-hydroxytryptamine (5-HT)7 receptor is the most recently identified serotonin receptor and is involved in a wide variety of central nervous system (CNS) functions, namely circadian rhythm, REM sleep, depression, thermoregulation, obsessive-compulsive disorder (OCD), anxiety, schizophrenia, epilepsy, nociception, migraine, sensation-seeking behavior, impulsivity, learning and memory. These numerous (patho)physiological processes of the CNS, in which the 5-HT7 receptor is involved, most likely reflect a diverse set of signaling pathways arising from this receptor. In order to reveal new interaction partners and possibly new signaling and/or trafficking pathways, we performed a yeast two-hybrid screening, using the C-terminal tail of the 5-HT7a receptor as bait and an adult-human brain cDNA library as prey. In this way we identified RhoBTB3 as a new interaction partner of the 5-HT7a receptor. By means of co-immunoprecipitation we were able to confirm the interaction between full length 5-HT7a receptor and RhoBTB3 in HEK293T cells. Subsequent domain mapping of this interaction revealed that not only the C-terminal tail, but also the third intracellular loop of the 5-HT7a receptor is involved. In addition, immunofluorescence microscopy showed clear co-localization between the 5-HT7a receptor and RhoBTB3 at the plasma membrane and in the endoplasmic reticulum. Despite the fact that RhoBTB3 has been shown to interact with Cul3, which in turn interacts with the E3 ubiquitin ligase, Roc1, we show here that RhoBTB3 neither recruits Cul3/Roc1 to the 5-HT7a receptor nor does it mediate ubiquitination of this receptor. Instead, we demonstrate that RhoBTB3 strongly inhibits proteasomal degradation of the 5-HT7a receptor. PMID:22245496
Matthys, Anne; Van Craenenbroeck, Kathleen; Lintermans, Bķatrice; Haegeman, Guy; Vanhoenacker, Peter
Discriminating between 5-HT3A and 5-HT3AB receptors
The 5-HT3B subunit was first cloned in 1999, and co-expression with the 5-HT3A subunit results in heteromeric 5-HT3AB receptors that are functionally distinct from homomeric 5-HT3A receptors. The affinities of competitive ligands at the two receptor subtypes are usually similar, but those of non-competitive antagonists that bind in the pore often differ. A competitive ligand and allosteric modulator that distinguishes 5-HT3A from 5-HT3AB receptors has recently been described, and the number of non-competitive antagonists identified with this ability has increased in recent years. In this review, we discuss the differences between 5-HT3A and 5-HT3AB receptors and describe the possible sites of action of compounds that can distinguish between them.
Thompson, AJ; Lummis, SCR
Effect of fluvoxamine on platelet 5HT2A receptors as studied by [3H]lysergic acid diethylamide ([3H]LSD) binding in healthy volunteers
Alterations in platelet 5-HT2A receptor characteristics have been reported in major depression as well as in other psychiatric diseases, and some effort\\u000a has been made to utilize platelet 5-HT2A receptor status as a biological correlate to antidepressant drug response. In order to investigate whether treatment with\\u000a a selective serotonin reuptake inhibitor affects platelet 5-HT2A receptors, we have studied platelet [3H]lysergic
O. Spigset; Tom Mj÷rndal
Overexpression of 5HT1B Receptor in Dorsal Raphe Nucleus Using Herpes Simplex Virus Gene Transfer Increases Anxiety Behavior after Inescapable Stress
5-HT1B autoreceptors have been implicated in animal models of stress and are regulated selectively by serotonin-selective reuptake inhibitors such as fluoxetine. These terminal autore- ceptors regulate serotonin release from dorsal raphe nucleus (DRN) projections throughout rat forebrain. However, it has not been previously possible to manipulate 5-HT1B autoreceptor activity selectively without also changing 5-HT1B activity in other neurons mediating different
Michael S. Clark; Timothy J. Sexton; Molly McClain; Daniel Root; Ruth Kohen; John F. Neumaier
Comparison of contractile responses to 5-hydroxytryptamine and sumatriptan in human isolated coronary artery: synergy with the thromboxane A2-receptor agonist, U46619.
1. The interaction between the thromboxane A2 receptor agonist, U46619 and two 5-hydroxytryptamine (5-HT) receptor agonists, the non-selective, naturally occurring agonist, 5-HT and the selective 5-HT1-like agonist, sumatriptan were studied in human epicardial coronary arteries in vitro. 2. Coronary artery rings (2-4 mm in diameter) were prepared from epicardial arteries from explant hearts of patients undergoing heart transplant (cardiomyopathy, n = 13; ischaemic heart disease, n = 10) and unused donor hearts (n = 5). Each ring of artery was set at optimal resting conditions to record changes in isometric force. 3. The majority of artery rings developed phasic, rhythmic contractions either spontaneously or in response to all vasoconstrictor agonists tested. Both the spontaneous and agonist-induced phasic contractions were abolished by nifedipine (0.1 microM). 4. Concentration-contraction curves to 5-HT-receptor agonists and noradrenaline (NA), were first constructed in artery rings that did not develop phasic activity. 5-HT and ergometrine were the most potent agonists with EC50 values of 6.8 +/- 0.2 and 7.7 +/- 0.2 (-log M) respectively. Potencies (EC50's) to sumatriptan, methysergide and noradrenaline could not be determined due to their poor ability to contract the coronary artery. Maximum contractions (Emax; normalized as a percentage of the contraction to a maximum-depolarizing concentration of K+ in physiological salt solution (KPSS)) for 5-HT, ergometrine, sumatriptan, methysergide and noradrenaline were 40 +/- 10, 9 +/- 3, < 5, < 5 and < 5% respectively. 5. In arteries without phasic activity, U46619 (1 nM) caused an increase in force of 3.8 +/- 1% KPSS.(ABSTRACT TRUNCATED AT 250 WORDS)
Cocks, T. M.; Kemp, B. K.; Pruneau, D.; Angus, J. A.
5-hydroxytryptamine-stimulated accumulation of 1,2-diacylglycerol in the rabbit basilar artery: a role for protein kinase C in smooth muscle contraction.
1. 5-Hydroxytryptamine (5-HT) produced a concentration-dependent increase in the membrane concentration of 1,2-diacylglycerol (DG) in the rabbit isolated basilar artery, but did not stimulate the hydrolysis of membrane phosphoinositide. 2. The 5-HT-induced accumulation of DG could be blocked with the putative phospholipase C inhibitor 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate (NCDC; 70 microM), but not with the protein kinase C inhibitor, 1-(5-isoquinolinesulphonyl)-2-methyl piperazine (H7; 50 microM). 3. Direct stimulation of protein kinase C with phorbol 12,13-dibutyrate (PDBu) produced sustained smooth muscle contraction which was fairly rapid in onset and could be reversed by H7 but not by NCDC. The inactive phorbol, 4 alpha phorbol 12,13-dideceonate, did not produce contraction in the basilar artery. 4. 5-HT-induced contractions (1 nM-100 microM) were blocked or greatly reduced in the presence of the protein kinase inhibitor H7 or polymyxin B, and with the phospholipase C inhibitor, NCDC. The concentrations of these inhibitors which abolished contraction to 5-HT, did not alter smooth muscle contraction produced in response to 30 mM K(+)-physiological salt solution (PSS). 5. These data suggest that DG production and the subsequent activation of PKC forms an important component of the cerebrovascular contractile response to 5-HT. As the DG does not appear to arise from membrane phosphatidylinositol, it appears that 5-HT can stimulate the production of this second messenger in cerebral arteries by a mechanism which is different from peripheral arteries. Images Figure 1
Clark, A. H.; Garland, C. J.
High-Throughput Multiplexed Transcript Analysis Yields Enhanced Resolution of 5-Hydroxytryptamine2C Receptor mRNA Editing ProfilesS?
RNA editing is a post-transcriptional modification in which adenosine residues are converted to inosine (adenosine-to-inosine editing). Commonly used methodologies to quantify RNA editing levels involve either direct sequencing or pyrosequencing of individual cDNA clones. The limitations of these methods lead to a small number of clones characterized in comparison to the number of mRNA molecules in the original sample, thereby producing significant sampling errors and potentially erroneous conclusions. We have developed an improved method for quantifying RNA editing patterns that increases sequence analysis to an average of more than 800,000 individual cDNAs per sample, substantially increasing accuracy and sensitivity. Our method is based on the serotonin 2C receptor (5-hydroxytryptamine2C; 5HT2C) transcript, an RNA editing substrate in which up to five adenosines are modified. Using a high-throughput multiplexed transcript analysis, we were able to quantify accurately the expression of twenty 5HT2C isoforms, each representing at least 0.25% of the total 5HT2C transcripts. Furthermore, this approach allowed the detection of previously unobserved changes in 5HT2C editing in RNA samples isolated from different inbred mouse strains and dissected brain regions, as well as editing differences in alternatively spliced 5HT2C variants. This approach provides a novel and efficient strategy for large-scale analyses of RNA editing and may prove to be a valuable tool for uncovering new information regarding editing patterns in specific disease states and in response to pharmacological and physiological perturbation, further elucidating the impact of 5HT2C RNA editing on central nervous system function.
Morabito, Michael V.; Ulbricht, Randi J.; O'Neil, Richard T.; Airey, David C.; Lu, Pengcheng; Zhang, Bing; Wang, Lily
Palonosetron versus first-generation 5-hydroxytryptamine type 3 receptor antagonists for emesis prophylaxis in patients undergoing allogeneic hematopoietic stem cell transplantation.
First-generation 5-hydroxytryptamine type 3 (5-HT3) receptor antagonists (RAs) are currently the standard of care for prophylaxis against allo-HSCT-induced emesis. However, the efficacy of this combination in allo-HSCT recipients is not entirely satisfying. We sought to compare the efficacy of first-generation 5-HT3 RAs with that of second-generation 5-HT3 RAs in emesis prevention in allo-HSCT recipients. A total of 51 consecutive patients undergoing allo-HSCT for various hematological diseases in our institution were retrospectively reviewed. Patients who received daily first-generation 5-HT3 RAs, and 60-h palonosetron for emesis prophylaxis were stratified into the standard (n?=?23) and palonosetron (n?=?28) groups, respectively. Emesis severity and rescue therapy requirements in patients between these two groups were compared. Our results showed patients in standard and palonosetron groups had comparable severity of both acute and delayed emesis. However, 52.2Ā% of the patients in the standard group required rescue therapy, compared to only 21.4Ā% of the patients in the palonosetron group (p?=?0.046). Subgroup analysis showed rescue therapy for acute emesis was required by 26.1Ā% of the patients in the standard group and by only 3.6Ā% of the patients in the palonosetron group (p?=?0.037). In conclusion, palonosetron and first-generation 5-HT3 RAs were at least equally effective in emesis prophylaxis for allo-HSCT recipients. Patients receiving palonosetron, especially for acute emesis, required rescue therapy less frequently than those receiving first-generation 5-HT3 RAs. PMID:24604014
Chou, Cheng-Wei; Chen, Yeh-Ku; Yu, Yuan-Bin; Chang, Kuang-Hsi; Hwang, Wen-Li; Teng, Chieh-Lin Jerry
Effects of divalent cations on responses of a sympathetic ganglion to 5-hydroxytryptamine and 1,1-dimethyl-4-phenyl piperazinium.
1 The effects of raising or lowering [Ca(2+)](o) or [Mg(2+)](o) on potential changes evoked by 5-hydroxytryptamine (5-HT) and by the nicotinic agonist, 1,1-dimethyl-4-phenyl piperazinium (DMPP) have been investigated.2 Changes in membrane potential were measured at the ganglion or in postganglionic axons by the sucrose-gap technique. The ganglionic response to both 5-HT and DMPP was a depolarization followed by an after-hyperpolarization (AH). AH decayed exponentially over most of its time course; the time constant of decay for 5-HT responses was 4.4 +/- 0.3 min (mean +/- s.e.mean, rate constant 0.23 min(-1)) and that for DMPP responses was not significantly different, being 3.9 +/- 0.3 min (rate constant 0.26 min(-1)).3 Increasing [Ca(2+)](o) to 5.1 or 7.6 mM caused some hyperpolarization of the ganglion, reduced the amplitude of depolarizations evoked by 5-HT by 29% and usually potentiated responses to DMPP (average 12%). Ca-free solutions caused a depolarization of the ganglion, increased the amplitude of depolarizations evoked by 5-HT by 23% and reduced that of depolarizations to DMPP by 32%. [Mg(2+)](o) 12.7 and 25.4 mM caused depolarizations of the ganglion and reduced the amplitude of depolarizations evoked by 5-HT by 34 and 84%, respectively, and those to DMPP by 10 and 75%, respectively. Mg-free solutions or low [Mg(2+)](o) caused a slow depolarization of the ganglion and reduced the amplitude of depolarizations to both 5-HT and DMPP by approx. 20%. Ca/Mg-free solutions produced a slow depolarization of the ganglion, increased the amplitude of depolarizations evoked by 5-HT by 78% and reduced those to DMPP by 58%.4 Increasing [Ca(2+)](o) reduced the amplitude of AH evoked by 5-HT by 50% and increased that to DMPP by 73%, while prolonging AH duration and increasing the time constant of decay. Ca-free solutions had complex effects on AH evoked by 5-HT, which were increased on average by 116%, and depressed AH evoked by DMPP; in both cases there was a decrease in the time constant of decay. [Mg(2+)](o) 12.7 mM reduced the amplitude of AH evoked by 5-HT more than that evoked by DMPP, and increased the rate of decline of the exponential phase. Low Mg solutions reduced in amplitude the AH evoked by 5-HT by 56% and the AH evoked by DMPP by 38%. The time constant of decay was increased. Ca/Mg-free solutions reduced AH amplitude in both 5-HT and DMPP responses. The effects on time constant are consistent with the generation of AH by an electrogenic sodium pump, the ATP-ase of which is Mg(2+)-dependent and inhibited by Ca(2+).5 Responses to 5-HT could be recorded from postganglionic axons and consisted of a rapid depolarization, sometimes followed by an AH whose time constant of decay was smaller than that of ganglionic responses. Full dose-response curves in control and test media could be obtained. In Ca/Mg-free solutions, 5-HT depolarizations were potentiated but no significant shift in the curve was observed.6 It is suggested that divalent cations modulate the coupling between 5-HT receptor and ion channel, an increase in [Ca(2+)](o) reducing the coupling or stabilizing the ion channel in the closed conformation. Ca(2+) and Mg(2+) may compete for the same binding site. This mechanism does not appear to be involved at nicotinic receptors and their related ion channels. PMID:6265020
Nash, H L; Wallis, D I
Calcineurin-dependent cofilin activation and increased retrograde actin flow drive 5-HT-dependent neurite outgrowth in Aplysia bag cell neurons
Neurite outgrowth in response to soluble growth factors often involves changes in intracellular Ca2+; however, mechanistic roles for Ca2+ in controlling the underlying dynamic cytoskeletal processes have remained enigmatic. Bag cell neurons exposed to serotonin (5-hydroxytryptamine [5-HT]) respond with a threefold increase in neurite outgrowth rates. Outgrowth depends on phospholipase C (PLC) ? inositol trisphosphate ? Ca2+ ? calcineurin signaling and is accompanied by increased rates of retrograde actin network flow in the growth cone P domain. Calcineurin inhibitors had no effect on Ca2+ release or basal levels of retrograde actin flow; however, they completely suppressed 5-HT¢dependent outgrowth and F-actin flow acceleration. 5-HT treatments were accompanied by calcineurin-dependent increases in cofilin activity in the growth cone P domain. 5-HT effects were mimicked by direct activation of PLC, suggesting that increased actin network treadmilling may be a widespread mechanism for promoting neurite outgrowth in response to neurotrophic factors.
Zhang, Xiao-Feng; Hyland, Callen; Van Goor, David; Forscher, Paul
Antagonist activity of meta-chlorophenylpiperazine and partial agonist activity of 8-OH-DPAT at the 5HT 7 receptor
This study compared the use of adapter G-proteins to link Gs coupled G-protein receptors to a Ca2+ signal, enabling high throughput functional studies using a fluorescent imaging plate reader (FLIPR, Molecular Devices).The pharmacological profile of the human 5-hydroxytryptamine (5-HT7) receptor was studied using the adapter G-proteins G?16 and Gqs5 and compared to previously published adenylyl cyclase and receptor binding data.
Martyn Wood; Mark Chaubey; Peter Atkinson; David R. Thomas
Increased Maternal Corticosterone Levels in Rats: Effects on Brain 5HT1A Receptors and Behavioral Coping With Stress in Adult Offspring
This study examined the consequences of elevated corticosterone levels in lactating rats on their offspring's serotonergic 5-hydroxytryptamine (5-HT)1A receptor system and behavioral coping with stress. The mothers received normal drinking water or water with corticosterone, which, via the milk, enters the circulation and brains of the pups. In adulthood, the corticosterone-nursed offspring showed a consistently more passive way of coping
Peter Meerlo; Katalin M. Horvath; Paul G. M. Luiten; Luciano Angelucci; Assia Catalani; Jaap M. Koolhaas
Essential role for orbitofrontal 5-HT1B receptors in OCD-like behavior and SRI response in mice
Background Perseveration and sensorimotor gating deficits are core features of obsessive-compulsive disorder (OCD). Serotonin 1B receptor (5-HT1BR) agonists exacerbate OCD symptoms in patients, and induce perseveration and sensorimotor gating deficits in mice. Serotonin reuptake inhibitors (SRIs), but not noradrenaline reuptake inhibitors (NRIs), reduce OCD symptoms following 4¢8 weeks of treatment. Using mice, we compared the effects of chronic SRI versus NRI treatment on 5-HT1BR-induced OCD-like behavior, and 5-HT1BR sensitivity in orbitofrontal-subcortical ōOCD circuitsö. Furthermore, we localized the 5-HT1BR population that mediates OCD-like behavior. Methods Mice chronically received the SRI clomipramine or the NRI desipramine and were examined for 5-HT1BR-induced OCD-like behavior, or 5-HT1BR binding and G-protein-coupling in caudate-putamen, nucleus accumbens, and orbitofrontal cortex. Separate mice were tested for OCD- or depression-like behavior following 4, 14, 21, 28 or 56 days of SRI treatment. Finally, OCD-like behavior was assessed following intra-orbitofrontal 5-HT1BR agonist infusion, or intra-orbitofrontal 5-HT1BR antagonist infusion coupled with systemic 5-HT1BR agonist treatment. Results Effective, but not ineffective, OCD treatments reduced OCD-like behavior in mice with a time-course that parallels the delayed therapeutic onset in OCD patients, and downregulated 5-HT1BR expression in the orbitofrontal cortex. Intra-orbitofrontal 5-HT1BR agonist infusion induced OCD-like behavior, and intra-orbitofrontal 5-HT1BR antagonist infusion blocked OCD-like effects of systemic 5-HT1BR agonist treatment. Conclusions These results indicate that orbitofrontal 5-HT1BRs are necessary and sufficient to induce OCD-like behavior in mice, and that SRI pharmacotherapy reduces OCD-like behavior by desensitizing orbitofrontal 5-HT1BRs. Our findings suggest an essential role for orbitofrontal 5-HT1BRs in OCD pathophysiology and treatment.
Shanahan, Nancy A; Velez, Lady P; Masten, Virginia L; Dulawa, Stephanie C
Involvement of 5HT1, 5HT2, and 5HT3 Receptors in the Mediation of the Prolactin Response to Serotonin and 5Hydroxytryptophan
Serotonin (5-HT) is involved in the neuroendocrine regulation of prolactin (PRL) secretion as a stimulator. Within the last decade several 5-HT receptor types have been identified, but their ndividual role in the mediation of the PRL response to 5-HT is only partly understood. We investigated in conscious male rats the effect of different 5-HT1, 5-HT2, and 5-HT3 receptor antagonists on
Henrik J°rgensen; Ulrich Knigge; J°rgen Warberg
Differentiation of 5-hydroxytryptamine2 receptor subtypes using sup 125 I-R-(-)2,5-dimethoxy-4-iodo-phenylisopropylamine and sup 3 H-ketanserin
The radioligand binding characteristics of 125I-R-(-)4-iodo-2,5-dimethoxyphenylisopropylamine (125I-R-(-)DOI) and 3H-ketanserin were compared in rat and bovine cortical membranes. In rat cortex, 125I-R-(-)DOI labels a relatively low density of binding sites (Bmax = 2.5 +/- 0.2 pmol/gm tissue) with high affinity (KD = 0.63 +/- 0.09 nM). In bovine cortex, specific binding of 125I-R-(-)DOI represents less than 20% of total binding at radioligand concentrations above 0.6 nM, and, therefore, the data cannot be analyzed adequately by Scatchard transformation. By contrast, 3H-ketanserin displays saturable, specific high-affinity binding in both rat cortex (KD = 1.0 +/- 0.1 nM; Bmax = 11 +/- 0.4 pmol/gm tissue) and bovine cortex (KD = 1.2 +/- 0.2 nM; Bmax = 5.3 +/- 0.4 pmol/gm tissue). Ki values for 30 drugs were determined for 125I-R-(-)DOI-labeled sites in rat cortex and 3H-ketanserin-labeled sites in bovine cortex. 5-Hydroxytryptamine (5-HT) displays 250-fold higher selectivity for the 125I-R-(-)DOI-labeled sites (Ki = 3.0 +/- 0.7 nM) than for the 3H-ketanserin-labeled sites (Ki = 750 +/- 50 nM). Structural congeners of R-(-)DOI display 80- to 160-fold higher affinity for the 125I-R-(-)DOI binding site than for the 3H-ketanserin-labeled binding site. d-LSD and putative 5-HT2 antagonists are approximately equipotent at both sites. Significant correlations were found between drug affinities for 125I-R-(-)DOI-labeled sites in rat cortex and putative 5-HT2A sites labeled previously by 77Br-R-(-)DOB (r = 0.93, p less than 0.01), putative 5-HT2B sites labeled by 3H-ketanserin in bovine cortex (r = 0.63, p less than 0.01), and 5-HT1C binding sites that have been characterized by other investigators (r = 0.78, p less than 0.01). No significant correlations were found between drug affinities for 125I-R-(-)DOI-labeled sites in rat cortex and 5-HT1A, 5-HT1B, 5-HT1D, or 5-HT3 sites, as determined by previous investigators.
McKenna, D.J.; Peroutka, S.J. (Stanford Univ., CA (USA))
Dopa decarboxylase exhibits low pH half-transaminase and high pH oxidative deaminase activities toward serotonin (5-hydroxytryptamine)
Dopa decarboxylase (DDC) catalyzes not only the decarboxylation of l-aromatic amino acids but also side reactions including half-transamination of d-aromatic amino acids and oxidative deamination of aromatic amines. The latter reaction produces, in equivalent amounts, an aromatic aldehyde or ketone (depending on the nature of the substrate), and ammonia, accompanied by O2 consumption in a 1 : 2 molar ratio with respect to the products. The kinetic mechanism and the pH dependence of the kinetic parameters have been determined in order to obtain information on the chemical mechanism for this reaction toward 5-hydroxytryptamine (5-HT). The initial velocity studies indicate that 5-HT and O2 bind to the enzyme sequentially, and that d-Dopa is a competitive inhibitor versus 5-HT and a noncompetitive inhibitor versus O2. The results are consistent with a mechanism in which 5-HT binds to DDC before O2. The pH dependency of log V for the oxidative deaminase reaction shows that the enzyme possesses a single ionizing group with a pK value of ?7.8 that must be unprotonated for catalysis. In addition to an ionizing residue with a pK value of 7.9 similar to that found in the V profile, the (V/K)5-HT profile exhibits a pK value of 9.8, identical to that of free substrate. This pK was therefore tentatively assigned to the ?-amino group of 5-HT. No titrable ionizing residue was detected in the (V/K)O2 profile, in the pH range examined. Surprisingly, at pH values lower than 7, where oxidative deamination does not occur to a significant extent, a half-transamination of 5-HT takes place. The rate constant of pyridoxamine 5?-phosphate formation increases below a single pK of ?6.7. This value mirrors the spectrophotometric pKspec of the shift 420¢384 nm of the external aldimine between DDC and 5-HT. Nevertheless, the analysis of the reaction of DDC with 5-HT under anaerobic conditions indicates that only half-transamination occurs with a pH-independent rate constant over the pH range 6¢8.5. A model accounting for these data is proposed that provides alternative pathways leading to oxidative deamination or half-transamination.
Bertoldi, Mariarita; Voltattorni, Carla Borri
5-HT6 receptors and Alzheimer's disease
During the past 20 years, the 5-HT6 receptor has received increasing attention and become a promising target for improving cognition. Several studies with structurally different compounds have shown that not only antagonists but also 5-HT6 receptor agonists improve learning and memory in animal models. A large number of publications describing the development of ligands for this receptor have come to light, and it is now quite evident that 5-HT6 receptors have great pharmaceutical potential in terms of related patents. However, 5-HT6 receptor functionality is much more complex than initially defined. According to the existing data, different cellular pathways may be activated, depending on the drug being used. This article reviews preclinical and clinical evidence of the effects that 5-HT6 receptor compounds have on cognition. In addition, the biochemical and neurochemical mechanisms of action through which 5-HT6 receptor compounds can influence cognition will be described. Overall, several 5-HT6-targeted compounds can reasonably be regarded as powerful drug candidates for the treatment of Alzheimer's disease.