serotonine

Serotonine, more commonly known in English as serotonin, is a monoamine neurotransmitter derived from the amino acid tryptophan. It is present in the brain and central nervous system as well as in the enteric nervous system and blood platelets. In some languages the spelling serotonine is used; in English the term serotonin is standard. It participates in a wide range of physiological processes, including mood regulation, appetite, sleep, and gastrointestinal function.

Biochemistry and distribution: Serotonin is synthesized in two steps from tryptophan, first by tryptophan hydroxylase to 5-hydroxytryptophan and then by aromatic L-amino acid decarboxylase to serotonin. It is stored in vesicles and released when neurons are activated. Peripherally, most of the body’s serotonin comes from enterochromaffin cells in the gut. After release, serotonin acts on various receptors and is cleared primarily by reuptake through the serotonin transporter (SERT). It is metabolized by monoamine oxidase A to 5-hydroxyindoleacetic acid (5-HIAA).

Receptors and functions: Serotonin acts on at least seven receptor families (5-HT1 through 5-HT7), most of which are G protein-coupled receptors; 5-HT3 is a ligand-gated ion channel. In the brain, serotonin influences mood, cognition, and sleep; in the periphery it regulates gastrointestinal motility, nausea, and vascular tone, and platelets release serotonin at sites of vascular injury to aid hemostasis.

Clinical relevance: Altered serotonin signaling is linked to depression, anxiety, and migraine, among other conditions. Selective serotonin reuptake inhibitors (SSRIs) increase synaptic serotonin and are commonly used to treat mood disorders. Excess serotonin can cause serotonin syndrome, a potentially serious condition. Diagnosis and treatment considerations often involve assessment of serotonin metabolism and receptor interactions.