The product of this gene belongs to the ligand-gated ion channel receptor superfamily. This gene encodes subunit A of the type 3 receptor for 5-hydroxytryptamine (serotonin), a biogenic hormone that functions as a neurotransmitter, a hormone, and a mitogen. This receptor causes fast, depolarizing responses in neurons after activation. It appears that the heteromeric combination of A and B subunits is necessary to provide the full functional features of this receptor, since either subunit alone results in receptors with very low conductance and response amplitude. Alternatively spliced transcript variants encoding different isoforms have been identified. Expressed in cerebral cortex, amygdala, hippocampus, and testis. Detected in monocytes of the spleen and tonsil, in small and large intestine, uterus, prostate, ovary and placenta. Belongs to the ligand-gated ionic channel (TC 1.A.9) family.