Serotonin 3A receptor (5-HT3A receptor)

The **Serotonin 3A receptor (5-HT3A receptor)** is a ligand-gated ion channel and a member of the pentameric ligand-gated ion channel (pLGIC) superfamily[7][9][1][4]. Unique among serotonin receptors, which are mostly G-protein-coupled, the 5-HT3A receptor forms a cation-selective ion channel responsible for fast excitatory neurotransmission in the central and peripheral nervous systems[2][7]. It assembles as a homopentamer of 5-HT3A subunits or as a heteropentamer with other 5-HT3 (B, C, D, E) subunits, but only homopentameric 5-HT3A forms are functional as stand-alone units[7]. Its primary biological roles include regulation of gut motility and control of the emetic reflex, making it a major therapeutic target for antiemetic drugs, especially in the setting of chemotherapy-induced, radiation-induced, and postoperative nausea and vomiting[6][3]. The 5-HT3A receptor is also implicated in pain, psychiatric disorders (anxiety, depression, psychosis), addiction, and some neurodegenerative diseases[9][3][6]. Drugs targeting this receptor, especially the "setron" class of antagonists, have revolutionized supportive care in oncology and have applications in GI and CNS diseases but can be associated with safety risks such as ischemic colitis and cardiac arrhythmias with some agents[6]. The molecular function of the receptor involves serotonin binding to an extracellular site, triggering a conformational change that opens the central ion pore and leads to neuron depolarization and excitation[1][7].

Other names

5-HT3A5-HT3aSerotonin type 3A receptor5-HT3 receptor (when referring specifically to the A subunit-containing form)HTR3A

Competitive antagonism at the serotonin binding site, blocking the action of endogenous serotonin (notably by "setron" class drugs) Allosteric modulation (drugs can also modulate activity via non-orthosteric sites)