5-hydroxytryptamine receptor 1B also known as the 5-HT1B receptor is a protein that in humans is encoded by the HTR1B gene. The 5-HT1B receptor is a 5-HT receptor subtype.

Tissue distribution and function

5-HT1B receptors are widely distributed throughout the central nervous system with the highest concentrations found in the frontal cortex, basal ganglia, striatum, and the hippocampus. The function of the 5-HT1B 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 and decreasing glutamatergic transmission by reducing miniature excitatory postsynaptic potential (mEPSP) frequency, respectively. In the hippocampus, a recent study has demonstrated that activation of postsynaptic 5-HT1B heteroreceptors produces a facilitation in excitatory synaptic transmission which is altered in depression. When the expression of 5-HT1B 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-HT1E. Outside of the CNS, the 5-HT1B receptor is also expressed on the endothelium of blood vessels, particularly in the meninges. Activation of these receptors results in vasoconstriction. The high distribution of vasoconstrictive 5-HT1B and 5-HT1D receptors around the brain makes them a valuable drug target for the treatment of migraines. Blocking 5-HT1B receptor signalling also increases the number of osteoblasts, bone mass, and the bone formation rate. Knockout mice lacking the 5-HT1B gene have been reported to have a higher preference for alcohol, although later studies failed to replicate such abnormalities in alcohol consumption. 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. 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).

Ligands

Agonists

Partial agonists

Antagonists and inverse agonists

Undetermined Action

Genetics

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.