Serotonin (5-HT) Signaling
Serotonergic neurotransmission modulating mood, sleep, appetite, and cognition.
Overview
Serotonin (5-hydroxytryptamine, 5-HT) is synthesized from tryptophan by tryptophan hydroxylase (TPH1 in periphery, TPH2 in brain) and aromatic amino acid decarboxylase. It signals through 14 receptor subtypes in 7 families (5-HT1-7), mostly GPCRs (except 5-HT3, a ligand-gated ion channel). Serotonin is cleared by SERT (serotonin transporter) and degraded by MAO. ~95% of body serotonin is in the gut (enterochromaffin cells), regulating motility and secretion.
Cellular Location
Raphe nuclei → widespread CNS projections; GI tract
Clinical Significance
SSRIs (fluoxetine, sertraline) are first-line antidepressants; triptans (5-HT1B/1D agonists) treat migraine; 5-HT3 antagonists (ondansetron) for nausea; psychedelics act on 5-HT2A.