In the field of neurochemistry, 5-HT receptors are receptors for the neurotransmitter and peripheral signal mediator serotonin, also known as 5-hydroxytryptamine or 5-HT. 5-HT receptors are located on the cell membrane of nerve cells and other cell types including smooth muscle in animals, and mediate the effects of serotonin as the endogenous ligand and of a broad range of pharmaceutical and hallucinogenic drugs. All 5-HT receptors reduce cyclic adenosine monophosphate (cAMP). 5-HT receptors effect the release and activity of other neurotransmitters such as glutamate, dopamine and GABA. 5-HT2A receptors increase the activity of glutamate in many areas of the brain, while some other serotonin receptors have the effect of suppressing glutamate. Increased stimulation of 5-HT2A receptors seem to oppose the therapeutic actions of increased stimulation of other serotonin receptors in anti-depressant and anxiolytic treatments. 
Note that there is no 5-HT1C receptor since, after the receptor was cloned and further characterized, it was found to have more in common with the 5-HT2 family of receptors and was redesignated as the 5-HT2C receptor.
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