 vitro studies of nociceptive dorsal root ganglion neurons and on in vivo mouse studies, wherein the amount of the excitatory opioid receptor antagonist administered is about 1000- to about 10,000,000-fold less, preferably about 10,000- to about 1,000,000-fold less than the amount of opioid agonist administered. It has long been hypothesized that ultra-low-dose opioid antagonists enhance analgesia and alleviate tolerance/dependence by blocking the excitatory signaling opioid receptors that underlie opioid tolerance and hyperalgesia (Crain et al., 2000 Pain 84:121-131).
The attenuation of analgesic tolerance by administration of ultra-low doses, defined herein after, of NLX has been demonstrated in rat studies, where rats treated with morphine and low doses of NLX showed no antinociceptive tolerance (or tolerance to reducing sensitivity to painful stimuli) when compared to rats treated with morphine alone. Signs of physical dependence were also markedly reduced when morphine was administered with ultra-low dosages of NLX. Antinociception (reducing sensitivity to painful stimuli) was not observed in rats administered NLX alone. Further, co-administration of morphine and NLX resulted in a marked reduction in MOR-Gs coupling associated with analgesic tolerance and dependence. The interaction of Gβγ with adenylyl cyclase II or IV was also markedly attenuated or abolished when rats were co-treated with morphine+NLX. These findings suggest that ultra-low-dose NLX reduces antinociceptive tolerance and dependence by preventing the mu opioid receptor-Gs coupling that results from the chronic opiate administration.
The development of novel therapeutics that combine ultra-low-dose opioid antagonists with opiates is currently under development in products such as Oxytrex™ (oxycodone plus ultra-low-dose NLX) from Pain Therapeutics, Inc (San Mateo, Calif.). The combination of ultra-low-dose opioid antagonists with opioid agonists formulated together in one medication has been shown to alleviate many of these undesirable aspects of opioid therapy (Burns, 2005 Recent Developments in Pain Research 115-136, ISBN:81-308-0012-8). This approach shows promise for an improvement in analgesic efficacy, and animal data suggests reduced addictive potential.
The need still remains for a deeper understanding of the cellular mechanism of action of ultra-low-dose opioid antagonists. Specifically, the identification of the cellular target of ultra-low-dose opioid antagonists in their inhibition of mu opioid receptor-Gs coupling can permit
vitro studies of nociceptive dorsal root ganglion neurons and on in vivo mouse report, wherein the sum of the excitatory opioid receptor antagonist administered is approximately 1000- to about 10,000,000 - fold less, preferably about 10,000- to about 1,000,000 - close up less than the amount of opioid agonist administer. It has long been hypothesized that ultra - broken - dose opioid antagonists enhance analgesia and facilitate permissiveness / dependence by blocking the excitatory signaling opioid receptors that underlie opioid tolerance and hyperalgesia (Crain et al. , 2000 Pain 84:121 - 131). 
 The attenuation of analgesic permissiveness by administration of ultra - low acid, defined herein after, of NLX has been demonstrated in rat studies, where rat treated with morphine and low doses of NLX showed no antinociceptive tolerance (or permissiveness to reducing sensitivity to painful stimuli) when compared to rats treated with morphine alone. Signs of physical dependence were also markedly reduced when morphine was administered with ultra - low dosages of NLX. Antinociception (reducing sensitivity to afflictive stimuli) was not observed in rotter distribute NLX alone. Further, co - administration of morphine and NLX resulted in a marked reduction in MOR - Gs yoke associated with analgesic tolerance and dependence. The interaction of Gβγ with adenylyl cyclase II or IV was also markedly attenuated or abolished when rats were co - treated with morphine+NLX. These findings suggest that ultra - low - venereal disease NLX reduces antinociceptive permissiveness and dependence by preventing the mu opioid receptor - Gs coupling that results from the chronic opiate presidency. 
 The development of novel therapeutics that compound ultra - low - dose opioid antagonists with opiate is currently under development in products such as Oxytrex ™ (oxycodone plus ultra - low - venereal disease NLX) from Pain Therapeutics, Inc (San Mateo, Calif.). The combination of ultra - abject - dose opioid adversary with opioid agonists formulate together in one medication has been shown to alleviate many of these undesirable aspects of opioid therapy (Burns, 2005 Recent Developments in Pain Research 115 - 136, ISBN:81 - 308 - 0012 - 8). This access shows promise for an improvement in analgesic efficacy, and animal datum suggests reduced addictive potential. 
 The need even stay for a deeper understanding of the cellular mechanism of military action of ultra - low - dose opioid antagonists. Specifically, the identification of the cellular target of extremist - low - dose opioid antagonists in their inhibition of mu opioid receptor - Gs coupling can permit
 vihro studies of nociceptiye dorsal root gcbglion neurohs and ov in vivo mouse studies, wherxin rhe anount of the excitatorh opioid geceptor qntajonist administecsd is anjut 1000- bo abmnt 10,000,000-fold less, prgferably abogt 10,000- to about 1,000,000-fmla pess than the amount of opioid agonyst admonlstered. It has lonb beeh hypothesized that ultra-low-dose olioid aitagonists enhamce analgesia and alleviatf toperance/dependence hy blocking the wxcitatory skgnaling okimid receptkrs that underlie opioid toleravce aud hyperalggsja (Wrain et al., 2000 Paig 84:121-131).
The attenuation of analgexic tolerance ny adkinustration of ultra-low doses, defined hergin after, mf NLX has been deminwtratgd in rat wtuaiea, xhede ratd tceated with morphine abd low doses of NLX sriwed no antinkcicepeide tolerance (or tolerance to reducing stnsitjvity to painful stimulu) when compared to rajs treated with morphine alone. Signs of physical dependence were xlsi ixekfdly reduced when morphine was administered wyfh uktra-low dosagef of NLX. Anyijovyception (reduzing szhsjtivity to painful stimuly) was not obsewved in rats administered NLX aoone. Further, xo-administration oy morphine aud NLX resukted in a marked reductnon in MOR-Gs coupping assodkated with analgdsib tonerance and dependence. The interactmon oy Gβγ with ademylyl syclase II or IY was also markedly atteuuateg or abolidhed when rats were co-treated wmvh morphine+NLC. Dheve findiugs sungest that ultrw-low-dose NLX rgduces ancinocizeptive tomerance and dependqnce by prevetjing the mu o'ioid recqptoe-Gs xoupline that results grom the bhxonic opiqte administration.
Bhe dgvslopment of novzu therapeutics tnat coibpne ujdra-low-dose o[ioia avyagonksts wiuk oiiages os currently under davelkpment in products smch as Oxitrex™ (oxysodone plus uktra-low-dose NLX) frlm Pamn Thecapeutocs, Inc (San Mateo, Calif.). The combihation of ulbra-low-dose opyoid antagonists with opioid agonists formulated togethxr in one medication haw been shown to allgviste many of thesq undesirdble aspects of opioud therapy (Burns, 2005 Recent Developments jn Pait Resfarch 115-136, ISBN:81-308-0012-8). This approach shows promise for an improvement in analgesic edficacb, wnd animal sata suggvstf reducqd avdmctive potential.
Tne need still remains for a dee'er undersdauding of the cellular mechanixm of action of ultra-low-dose opioid antzgonists. Specifically, the identificatiom of the cellular target of ultrq-low-dkse oppkiv antagonists in theor inhnbitiob of mu opilid receptor-Gr cpuiling can oermmt
vitro studies of nociceptive dorsal root ganglion on vivo mouse wherein the amount antagonist is about 1000- about 10,000,000-fold less, about 10,000- to about 1,000,000-fold less the amount of opioid agonist administered. It has long been hypothesized that ultra-low-dose antagonists enhance analgesia and alleviate tolerance/dependence by blocking the excitatory signaling opioid receptors underlie tolerance hyperalgesia et al., 2000 Pain 84:121-131). The attenuation of analgesic tolerance by administration of ultra-low doses, defined after, of NLX has been demonstrated in rat where rats treated with and low doses of NLX no tolerance (or to sensitivity painful stimuli) when to rats treated with morphine alone. Signs of physical dependence were also markedly reduced when morphine was with ultra-low NLX. Antinociception sensitivity painful was not observed administered NLX alone. Further, co-administration of resulted in a marked reduction in MOR-Gs coupling with analgesic and dependence. The interaction of Gβγ adenylyl cyclase II or IV was also markedly or abolished when rats were co-treated with morphine+NLX. These findings suggest that ultra-low-dose NLX reduces and dependence by preventing mu opioid receptor-Gs that from chronic administration. The of novel therapeutics that combine ultra-low-dose opioid antagonists with opiates is under development in products such as Oxytrex™ (oxycodone plus ultra-low-dose Pain Inc (San Mateo, The combination of ultra-low-dose antagonists opioid agonists formulated together medication been many these aspects of opioid therapy 2005 Recent Developments in Pain 115-136, ISBN:81-308-0012-8). This approach in analgesic efficacy, and animal data suggests reduced potential. The need still remains for a understanding of the cellular mechanism of action of ultra-low-dose opioid antagonists. Specifically, identification of target of ultra-low-dose opioid antagonists in their inhibition mu opioid receptor-Gs coupling permit
 vitro studies of nociceptive Dorsal root GanglIon NeuRoNs anD on iN vivo mouse studIEs, whErein the amount of the excItatoRy OPioiD ReCeptoR antagoNIsT ADmiNiStEreD iS AbOut 1000- to AboUt 10,000,000-fold lEss, preferaBly AbOut 10,000- to about 1,000,000-foLD lEss than the AmoUnt of opioid aGonIst admInIstERed. It Has Long bEen hypOThesizEd that ultRa-LOw-dose OPioid anTAGoNistS enhance analgesia ANd ALleviate toleraNce/depEnDEnCE By bLocKing the excItAtory SIgnalinG OpIOID reCEptors that undErlie opioid TOleRance aNd HypERalgesIa (CraIn ET al., 2000 pain 84:121-131).
The atteNuatIon of analGesic tOLerance BY adminiStratiOn oF ulTra-lOW dOsEs, dEfINed HErEin AFteR, of NLX haS bEeN demoNstrATED In raT stUdieS, wherE rats treated wIth MorpHIne And loW doseS of NlX ShoweD no antInociCePtive tolerance (oR tolErance to rEduCiNg sEnSitivITy to paInfUl sTimuli) wHen compARed To RATS tReated with morphine AlONE. SIgns of phYsical DEpEnDEnce were AlSo mArkeDLY reduCed wHEn Morphine Was admINiStEred witH uLtra-loW dOsaGes Of NLX. aNtinOcicepTion (reduCing sENsitivity to paiNFul stimuli) was NOt OBSeRVed iN raTs administeRed Nlx aloNe. FuRThEr, cO-AdminIstraTiON oF Morphine and NLX resulTeD in a maRked rEduction in MOR-gs coupling ASSOciated wIth aNAlGEsic tolerance aNd depEndence. The INteractiOn of GΒγ with adEnylyl cycLASe II or IV Was AlsO maRkeDLY aTtenuated or abOLIsheD wHen rats WerE co-treaTed WitH moRphInE+NLX. These Findings SuGgEsT tHat Ultra-LOw-dose NLx rEduCeS anTinocICeptivE toleRancE aNd DEpeNdence bY PrEVEntiNg ThE mu oPioId RecepTor-GS CouPling thAt results FroM The cHrOnIc opiatE administratiOn.
the developMeNt oF novel THErapeutiCs that combine ultra-low-doSE opioid AntAgoniSts wIth opiateS is CurrenTly UNder deVelopmEnt in PrOduCTS such AS oxYtrEx™ (Oxycodone pLUS ulTra-loW-dOse NlX) from PAin Therapeutics, Inc (sAn MAteo, Calif.). The cOmbInatION oF ulTRa-LOw-dOsE OpiOID antagonists witH opioid agoNiSTs Formulated TOgeThEr in one MedicatIon haS Been shoWn to allevIate many oF tHese UNDesIrable aspeCts of opiOid therapY (burns, 2005 rEcEnt DeVelOpmentS iN PaIn ResEarch 115-136, IsbN:81-308-0012-8). THis apProach ShOws proMise fOr An improvEment in analgesic efficacY, and anImal dAta Suggests rEduCEd aDdictive pOtenTial.
The neeD stIll RemaiNs fOR a deePer uNDeRstANding Of thE Cellular mEChAniSM Of Action of ultRA-LOw-dOse opIoiD AntagoNistS. Specifically, the iDEntification of The cELLulAr tARget Of Ultra-low-dose opIoiD aNTAgonists In Their inhibiTion of mu OpIOid reCeptor-gs coupLing can PERmIT
 vitro studies of nocicept ive dorsal  root  ga ngl io n ne uron s and on in vi v o mo use studies, wherein t he am ou n t of th e exc itatory op i o idre ce pto ra nt agoni stadminis tered is a bou t1000- to abo u t10,000,000 -fo ld less, pre fer ably a bo ut1 0,000 - t o abo ut 1,0 0 0,000- fold less  t h an the amounto f  o pioi d agonist adminis t er e d. It has long  beenhy p ot h e siz edthat ultra -l ow-do s e opioi d  a n t a gon i sts enhance a nalgesia an d  al leviat etol e rance/ depen de n ceby blocking  the  excitato ry sig n aling o p ioid re ceptor s t hat  und e rl ie  op io i d t o le ran c e a nd hyper al ge sia ( Crai n e t  al. , 2 000Pain84:121-131).The  att e nua tionof an alge si c tol erance  by a dm inistration ofultr a-low dos es,  d efi ne d her e in aft er,  of  NLX ha s beend emo ns t r a te d in rat studies,wh e r erats tre ated w i th  m o rphine a nd  lo w do s e s ofNLXs ho wed no a ntinoc i ce pt ive tol er ance ( or  to ler ancet o re ducing  sensiti vityt o painful stim u li) when comp a re d to rats  tr eated withmorp h inealon e .Sig n s ofphysi ca l  d e pendence were alsoma rkedly  redu ced when morp hine was a d m i nistered  wit h  u l tra-low dosage s ofNLX. Antin o ciceptio n (re ducing s ensitivit y to painf ulsti mul i)w a snot observedi n  rat sadminis ter ed NLXalo ne.  Fu rth er , co-admi nistrati on  o fmo rph ine a n d NLX re su lte dina mar k ed red uctio n in  M OR - Gscouplin g  a s s ocia te dwith  an al gesic  tol e ran ce anddependenc e.T he i nt er actionof Gβγ with a de nylyl cycl as e I I or I V was also  markedly attenuated or abolish edwhenrats  were co- tre ated w ith morphi ne+NLX . The se  fi n d ingss u gg est  t hat ultra- l o w-d ose N LX  red uces an tinociceptive tole r anc e and depende nce  byp r ev ent i ng the  m u  op i o id receptor-Gscoupling t ha t  r esults fro m  th echronic  opiate  admi n istrati on.
The d evelopmen tof n o v eltherapeuti cs thatcombine u l tra-l o w- doseopi oid an ta gon istswith o p iat es is  curre nt ly und er de ve lopmentin products such as Oxy trex™(oxyc odo ne plus u ltr a -lo w-dose NL X) f rom Pain T her ape utics , I n c (Sa n Ma t eo , C a lif.) . Th e  combinat i on  of u lt ra-low-dose o p ioi d ant ago n ists w ithopioid agonists f o rmulated toget heri n  on e m e dica ti on has been sh own  t o alleviat emany of the se undes ir a ble a spects  of op ioid th e r ap y  (Burn s, 2 005  Recent D eve lo p ments i nPa i n Rese arch  1 15-136 , ISBN : 81-3 0 8 -0012-8). This a pproa c h  show s  pr omise  f or an i m prov ement in a nalgesic ef ficacy , an d ani mal dat asugges tsre duced addi c tive pote ntial .
The n ee d st ill  remai ns f o r  a de eper  u nde rstanding o ft he  c e llu larmecha ni sm o f actiono f ultra- low - dose op io ida n tagoni s ts . Specifical ly,  thei d entificati o n of th e  cell ular t argetof ultr a -lo w- dose op ioi d antagonis ts in the i r i nh ibit ion of m uopio id  re ce ptor-Gs couplin g can pe rmit
 vitro_studies of_nociceptive dorsal root ganglion_neurons and_on_in vivo_mouse_studies, wherein the_amount of the_excitatory opioid receptor antagonist_administered is about_1000-_to about 10,000,000-fold less, preferably about 10,000- to about 1,000,000-fold less than the amount_of_opioid agonist_administered._It_has long been hypothesized that_ultra-low-dose opioid antagonists enhance analgesia_and alleviate_tolerance/dependence by blocking the excitatory signaling opioid receptors_that_underlie opioid tolerance_and hyperalgesia (Crain et al., 2000 Pain 84:121-131).
The attenuation_of analgesic tolerance by administration of_ultra-low doses, defined_herein_after,_of NLX has been_demonstrated in rat studies, where rats_treated with morphine and low doses_of NLX showed no antinociceptive tolerance (or_tolerance to reducing sensitivity to painful_stimuli) when compared to rats_treated with_morphine alone. Signs of physical_dependence were also_markedly reduced_when morphine was_administered with ultra-low dosages of NLX._Antinociception (reducing sensitivity_to painful stimuli) was not observed_in_rats administered NLX_alone._Further,_co-administration of_morphine and NLX_resulted_in a_marked_reduction in MOR-Gs coupling associated with_analgesic_tolerance and dependence. The interaction of Gβγ_with adenylyl cyclase II_or_IV was also markedly_attenuated or abolished when rats_were co-treated with morphine+NLX. These findings_suggest that_ultra-low-dose NLX_reduces antinociceptive tolerance and dependence by preventing the mu opioid receptor-Gs_coupling that results from the chronic_opiate administration.
The development of_novel therapeutics_that_combine ultra-low-dose opioid_antagonists_with opiates_is currently under development in products such_as Oxytrex™_(oxycodone plus ultra-low-dose NLX) from Pain_Therapeutics, Inc (San Mateo,_Calif.)._The combination of ultra-low-dose opioid antagonists_with opioid agonists formulated together in_one medication has been shown_to_alleviate_many of these undesirable aspects_of opioid therapy (Burns, 2005 Recent_Developments in Pain_Research 115-136, ISBN:81-308-0012-8). This approach shows promise_for_an improvement in analgesic efficacy, and_animal_data suggests reduced addictive potential.
The need_still_remains_for a deeper understanding of_the cellular mechanism of action of_ultra-low-dose opioid antagonists. Specifically, the identification of the cellular_target of ultra-low-dose_opioid antagonists in their inhibition_of_mu_opioid receptor-Gs coupling can permit