HTR3B

HTR3B is a human gene that encodes the 5-hydroxytryptamine receptor 3B (5-HT3B) subunit of the serotonin receptor 3 family. 5-HT3 receptors are pentameric ligand-gated ion channels that mediate fast excitatory neurotransmission in response to serotonin. The 5-HT3B subunit does not form functional channels on its own but co-assembles with the 5-HT3A subunit to form heteromeric pentamers with distinct pharmacological and biophysical properties compared with 5-HT3A homomers.

Expression of HTR3B transcripts is observed in various regions of the central nervous system and in the enteric nervous system, with notable presence in the brain and gastrointestinal tract. The receptor complex participates in modulating nausea and vomiting, gastrointestinal motility, pain processing, and aspects of mood and anxiety.

Clinical significance and pharmacology related to HTR3B have been explored in relation to several conditions, including irritable bowel syndrome, migraine, and anxiety disorders. Findings across studies have been variable and not always conclusive. Because 5-HT3 receptors are targets of antiemetic and anti-nausea medications, genetic variation in HTR3B may influence therapeutic responses to these drugs in contexts such as chemotherapy-induced nausea or IBS-related symptoms, though evidence remains inconclusive.

HTR3B belongs to the Cys-loop ligand-gated ion channel superfamily. In humans, it forms functional receptor complexes with other subunits, notably HTR3A, contributing to the diversity of 5-HT3 receptor signaling involved in both nervous system and gut function.