transporter, as acetylcholine is terminated via rapid metabolism into choline by cholinesterase enzymes, and choline is subsequently transported back into the cell and reconverted into acetylcholine. Transporters associated with histamine and the endocannabinoids have not yet been identified. Clinical significance A variety of neurotransmitter reuptake transporters are pharmacotherapeutic targets for modulating the synaptic neurotransmitter concentration, and therefore neurotransmission. Antidepressants such as SSRIs, SNRIs and TCAs suppress the activity of serotonin and/or norepinephrine transporters, preventing the reuptake of targeted neurotransmitters from the synaptic cleft. Psychostimulants like cocaine, amphetamines, and methylphenidate act by inhibiting and/or reversing the dopamine and/or norepinephrine transporters. Some dissociatives like phencyclidine and ketamine are also dopamine transporter inhibitors. Tiagabine, a drug used as an anticonvulsant, acts by inhibiting the GABA transporter 1. Vesicular transporters could provide an alternative therapeutic target for the modulation of chemical neurotransmission, as the activity of these transporters could affect the quantity of neurotransmitter released. Vesamicol, for example, is an inhibitor of the vesicular acetylcholine transporter. It prevents the loading of ACh into the presynaptic vesicles, causing a fall in the amount that is released in response to a neuronal action potential. It is not used clinically, but provides a useful tool for research into the behaviour of neurotransmitter vesicles. References External links Clearing Your Mind of Neurotransmitters: Functional Impact of Neurotransmitter Transporter Gene Variants - a videocast of the lecture by Randy Blakely, Ph.D., Vanderbilt University. Part of NIH Neuroscience Seminar series. 450 Mb file, .m4v format. The Blakely Lab - Laboratory exploring the molecular basis for neurotransmitter transporter structure, function and regulation. Integral membrane proteins