Serotonin receptors

There are a lot of subtypes of serotonin receptor and all except the 5-HT3 receptor are GPCRs. The 5-HT1 subtypes reduce the cAMP, whereas the 5-HT4 and 5-HT7 subtypes increase the cAMP. The 5-HT2 subtypes are attached through Gq to the phospholipase C therefore are excitatory by increasing the inositol trisphosphate and diacylglycerol. The 5-ht5and 5-ht6 subtypes are presently putative.

The 5-HT3 receptors are ligand-gated ion channels similar to the nicotinic receptor and form the pentamers. There are numerous isoforms. As cation conductances they mediate rapid depolarization and are distributed broadly in the nervous system. The numbers of drugs which bind to nicotinic receptors also bind to 5-HT3 receptors but there are selective antagonists at few isoforms (example, ondansetron). These are anti-emetics as they block 5-HT3 receptors in the region postrema, the chemosensitive cells of which the trigger vomiting in response to toxins in the blood.

Mainly 5-HT1, 5-HT2, and 5-HT3 receptor subtypes are positioned postsynaptically but 5-HT1A autoreceptors reduce the release of serotonin. The agents that reduce serotonin transmission—5-HT2 and 5-HT3 antagonists, and 5-HT1A agonists—have verified to be potent antianxiety agents.