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Definition: Serotonin is an indolamine neurotransmitter.

Serotonin: a.k.a 5-HT (abreviation); 5-hydroxytryptamine; enteramine; thrombocytin; thrombotonin; vasostatin.
Definition: Serotonin is an indolamine neurotransmitter.
Structure: 3-(2-aminoethyl)-5-indolamine; C10H12N2O
Properties
Serotonin is a(n) indolamine monamine neurotransmitter
Serotonin is involved in:
depression and other affective disorders
migraine headache
obsessive-compulsive disorder (OCD)
panic and other anxiety disorders
gastrointestinal function
vasoconstriction

Synthesis / Termination
Serotonin is synthesized from tryptophan which is first hydroxylated to 5-hydroxytryptophan by the rate-limiting enzyme tryptophan-5-hydroxylase. The intermediate is then decarboxylated by the nonspecific aromatic L-amino acid decarboxylase to serotonin.

The action of serotonin in the synapse is terminated by diffusion and reuptake at selecteive sites
Most serotonin is degraded by monoamine oxidase through oxidative demamination. Some of the resultant motabolite may oxidized further by a non-specific aldehyde dehydrogenase. The metabolites are then excreted in the urine.
Drugs
Agonists
tryptophan - increasing dietary intake of tryptophan can increase serotonin concentrations.
selective serotonin reuptake inhibitors (SSRI) - increases action of serotonin by increasing synaptic concentration.

tricyclic anti-depressants non-selectively block monoamine reuptake sites and increases action of serotonin by increasing synaptic concentration.
Antagonists: cyprohepatadine  ergotamine ketanserin  LSD  2-bromo-LSD  methylsergide  reserpine - causes depletion from vesicles