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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.[1] 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. 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. [1]

Classification[edit | edit source]

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.

Families[edit | edit source]

Family Type Mechanism
5-HT1 Gi/Go coupled decreasing cellular levels of cAMP
5-HT2 Gq/G11 coupled increasing cellular levels of inositol trisphosphate (IP3) and diacylglycerol (DAG)
5-HT3 ligand-gated Na+ and K+ cation channel depolarizing plasma membrane
5-HT4 Gs coupled increasing cellular levels of cAMP
5-HT5A G protein coupled; the primary coupling appears to be through Gi/o inhibiting adenylate cyclase activity.[2]
5-HT7 Gs coupled increasing cellular levels of cAMP

Specific proteins/genes[edit | edit source]

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

Summary of characterized 5-HT receptors, with selected high affinity agonist and antagonist ligands
Receptor Gene Actions Agonists Antagonists
  • CNS: neuronal inhibition, behavioural effects (sleep, feeding, thermoregulation, aggression, anxiety)
  • 5-(Nonyloxy)tryptamine,[3]
  • sumatriptan
  • methiothepin
  • yohimbine
  • metergoline
  • ergotamine
  • stomach: contraction
  • CNS, PNS: neuronal excitation, anxiety, emesis
  • 2-methyl-5-HT
5-HT4 HTR4
  • GIT: gastrointestinal motility
  • CNS: neuronal excitation, learning, memory
  • GR113808
  • Piboserod
5-HT5A HTR5A unknown
5-HT6 HTR6
  • CNS: unknown
  • LSD
SB271046 [5]
5-HT7 HTR7
  • CNS, GIT, blood vessels: unknown
  • 5-carboxytryptamine
  • LSD

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.

Therapeutic modulation[edit | edit source]

Various drugs are used to modulate the 5-HT system including some antidepressants, anxiolytics, antiemetics, antipsychotics and anti-migraine agents.

References & Bibliography[edit | edit source]

  1. Hoyer D, Clarke DE, Fozard JR, Hartig PR, Martin GR, Mylecharane EJ, Saxena PR, Humphrey PP (1994). International Union of Pharmacology classification of receptors for 5-hydroxytryptamine (Serotonin). Pharmacol. Rev. 46 (2): 157–203.
  2. 2.0 2.1 Nelson DL (2004). 5-HT5 receptors. Current drug targets. CNS and neurological disorders 3 (1): 53–8.
  3. Glennon RA, Hong SS, Dukat M, Teitler M, Davis K (1994). 5-(Nonyloxy)tryptamine: a novel high-affinity 5-HT1D beta serotonin receptor agonist. J. Med. Chem. 37 (18): 2828–30.
  4. Rang, H. P. (2003). Pharmacology, Edinburgh: Churchill Livingstone. Page 187
  5. Target Schizophrenia - Possible future developments. URL accessed on 2007-07-06.

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