5-HT receptor

From Academic Kids

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 in animals and mediate the effects of serotonin as the endogenous ligand and of a broad range of pharmaceutical and recreational drugs. With the exception of the 5-HT3 receptor, a ligand gated ion channel, all other 5-HT receptors are G_protein coupled seven transmembrane (or heptahelical) receptors that activate an intracellular second messenger cascade.

  • 5-HT2 receptors are Gq/G11 coupled, mediating cellular effects through increasing cellular levels of inositol trisphosphate (IP3) and diacylglycerol (DAG). Three subtypes exist, namely 5-HT2A, 5-HT2B, and 5-HT2C (formerly called 5-HT1C).
  • The 5-HT4 receptor is Gs coupled, mediating cellular effects through increasing cellular levels of cAMP.
  • The 5-HT7 receptor is Gs coupled, mediating cellular effects through increasing cellular levels of cAMP.

Characterised 5-HT receptors

Within these general classes of 5-HT receptors, a number of specific types have been characterized:

Summary of characterised 5-HT receptors, with selected agonist/antagonist agents
receptor actions agonists antagonists
5-HT1A CNS: neuronal inhibition, behavioural effects (sleep, feeding, thermoregulation, anxiety) buspirone spiperone, methiothepin, ergotamine, yohimbine
5-HT1B CNS: presynaptic inhibition, behavioural effects; vascular: pulmonary vasoconstriction ergotamine, sumatriptan methiothepin, yohimbine, metergoline
5-HT1D CNS: locomotion; vascular: cerebral vasoconstriction sumatriptan methiothepin, yohimbine, metergoline, ergotamine
5-HT2A CNS: neuronal excitation, behavioural effects; smooth muscle: contraction, vasoconstriction / dilatation; platelets: aggregation α-methyl-5-HT, LSD (CNS) ketanserin, cyproheptadine, pizotifen, LSD (PNS)
5-HT2B stomach: contraction α-methyl-5-HT, LSD (CNS) yohimbine, LSD (PNS)
5-HT2C CNS, choroid plexus: cerebrospinal fluid (CSF) secretion α-methyl-5-HT, LSD (CNS) mesulergine, LSD (PNS)
5-HT3 CNS, PNS: neuronal excitation, anxiety, emesis 2-methyl-5-HT metoclopramide (high doses), renzapride, ondansetron, alosetron
5-HT4 GIT, CNS: neuronal excitation, gastrointestinal motility 5-methoxytryptamine, metoclopramide, renzapride, tegaserod GR113808
5-ht5 CNS: unknown unknown unknown
5-ht6 CNS: unknown unknown unknown
5-HT7 CNS, GIT, blood vessels: unknown 5-carboxytryptamine, LSD methiothepin

Note that there is no 5-HT1C receptor since, after the receptor was cloned and further characterised, 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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