<Tr> <Td_colspan="2"> Infobox references </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> </Tr> <P> Serotonin (/ ˌsɛrəˈtoʊnɪn, ˌsɪərə - /) or 5 - hydroxytryptamine (5 - HT) is a monoamine neurotransmitter . Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract (GI tract), blood platelets, and the central nervous system (CNS) of animals, including humans . It is popularly thought to be a contributor to feelings of well - being and happiness . </P> <P> Approximately 90% of the human body's total serotonin is located in the enterochromaffin cells in the GI tract, where it is used to regulate intestinal movements . The serotonin is secreted luminally and basolaterally which leads to increased serotonin uptake by circulating platelets and activation after stimulation, which gives increased stimulation of myenteric neurons and gastrointestinal motility . The remainder is synthesized in serotonergic neurons of the CNS, where it has various functions . These include the regulation of mood, appetite, and sleep . Serotonin also has some cognitive functions, including memory and learning . Modulation of serotonin at synapses is thought to be a major action of several classes of pharmacological antidepressants . </P>

Where is serotonin produced in the human body
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