Serotonin

5-HT is also called serotonin, which is derived from tryptophan. Tryptophan is formed by tryptophan hydroxylase to form 5-hydroxytryptophan, and then decarboxylase to 5-HT. 5-HT is a central nervous system delivery substance, the active part of which is indoleamine. It is widely present in the brain, platelets, stomach and other tissues, with the largest content in the brain, and is a strong smooth muscle stimulator and vasoconstrictor. It is high in platelets, and participates in vasoconstriction after platelet rupture and release. Two-thirds of 5-HT is excreted after the liver is combined with sulfuric acid or glucuronic acid, or indole is cleaved and decomposed; about one-third is oxidized and deaminated by monoamine oxidase to form 5-HLAA and excreted from urine. 5-HIAA is the final product of 5-hydroxytryptophan metabolism and has no biological activity.