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5-HT_1B receptors are widely distributed throughout the central nervous system with the highest concentrations found in the frontal cortex, basal ganglia, striatum, and the hippocampus.^[8] The function of the 5-HT_1B receptor differs depending upon its location. In the frontal cortex, it is believed to act as a terminal receptor inhibiting the release of dopamine. In the basal ganglia and the striatum, evidence suggests 5-HT signaling acts on an autoreceptor, inhibiting the release of serotonin^[9] and decreasing glutamatergic transmission by reducing miniature excitatory postsynaptic potential (mEPSP) frequency,^[10] respectively. In the hippocampus, a recent study has demonstrated that activation of postsynaptic 5-HT_1B heteroreceptors produces a facilitation in excitatory synaptic transmission which is altered in depression.^[11] When the expression of 5-HT_1B in human cortex was traced throughout life, significant changes during adolescence were observed, in a way that is strongly correlated with the expression of 5-HT_1E.^[12]

Outside of the CNS, the 5-HT_1B receptor is also expressed on the endothelium of blood vessels, particularly in the meninges.^[13] Activation of these receptors results in vasoconstriction. The high distribution of vasoconstrictive 5-HT_1B and 5-HT_1D receptors around the brain makes them a valuable drug target for the treatment of migraines.^[13]

Blocking 5-HT_1B receptor signalling also increases the number of osteoblasts, bone mass, and the bone formation rate.^[14]

Knockout mice lacking the 5-HT_1B gene have been reported to have a higher preference for alcohol, although later studies failed to replicate such abnormalities in alcohol consumption.^[15] These mice have also been reported to have a lower measure of anxiety (such as on the elevated plus maze test) and a higher measure of aggression.^[15]

Under basal conditions, knockout mice present with a "normal" phenotype and exhibit a sucrose preference (lack of sucrose preference is considered a measure of anhedonia). However, after undergoing chronic unpredictable stress treatment to induce a "depression-like" phenotype these animals do not benefit from administration of selective serotonin reuptake inhibitor (SSRIs).^{[11][failed verification]}

Activation of the serotonin 5-HT_1B receptor appears to mediate the prosocial effects of entactogens acting as serotonin releasing agents like MDMA in animals.^{[16][17][18][19]} In addition, serotonin 5-HT_1B receptor activation appears to mediate the locomotor hyperactivity of these agents.^[20][21][22] The serotonin 5-HT_1B receptor also appears to be required for the persisting antidepressant- and anxiolytic-like effects as well as acute hypolocomotion of the serotonergic psychedelic and non-selective serotonin receptor agonist psilocybin in animals.^[23]

• Dextromethorphan^[27]

In humans the protein is coded by the gene HTR1B.

A genetic variant in the promoter region, A-161T, has been examined with respect to personality traits and showed no major effect.^[28]

• 5-HT₁ receptor
• 5-HT receptor

• "5-HT_1B". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology.
• Human HTR1B genome location and HTR1B gene details page in the UCSC Genome Browser.
• Overview of all the structural information available in the PDB for UniProt: P28222 (5-hydroxytryptamine receptor 1B) at the PDBe-KB.

This article incorporates text from the United States National Library of Medicine, which is in the public domain.