ABSTRACT
Serotonin is a monoamine neurotransmitter primarily present in the enterochromaffin cells of gastrointestinal tract, central nervous system (CNS), blood platelets and of gastrointestinal mucosa. Serotonin present in CNS is responsible for a number of behavioral functions, including the regulation of mood, sleep or wakefulness, appetite, nociception, and sexual behavior. Serotonin exerts its effects through a variety of membrane-bound receptors, present in the central and peripheral nervous system, and in nonneuronal tissues in the gut, cardiovascular system and blood. It belongs to a complex family of neurotransmitters consisting of seven families of 5-hydroxytryptamine (5-HT) (5-HT1–15-HT7) receptors, and at least 14 different serotonin receptor subtypes. Except for 5-HT3 receptor, which is a ligand-gated ion channel mediating fast depolarization, all other 5-HT receptors belong to the G-protein-coupled receptor superfamily. These receptors are classified according to their structure, their pharmacology and the transduction signal initiated by them.
