![]() ![]() ![]() There follows oxidation by aldehyde dehydrogenase to 5-hydroxyindoleacetic acid ( 5-HIAA), the indole acetic-acid derivative. The rate-limiting step is hydride transfer from serotonin to the flavin cofactor. Metabolism involves first oxidation by monoamine oxidase to the corresponding aldehyde. Serotonin primarily acts through its receptors and its effects depend on which cells and tissues express these receptors. Despite its longstanding prominence in pharmaceutical advertising, the myth that low serotonin levels cause depression is not supported by scientific evidence. In plants serotonin synthesis seems to be associated with stress signals. In less complex animals, such as some invertebrates, serotonin regulates feeding and other processes. Serotonin is involved in numerous physiological processes, including sleep, thermoregulation, learning and memory, pain, (social) behavior, sexual activity, feeding, motor activity, and biological rhythms. Serotonin also forms several salts, including pharmaceutical formulation of serotonin adipate. Serotonin crystallizes in P2 12 12 1 chiral space group forming different hydrogen-bonding interactions between serotonin molecules via N-H.O and O-H.N intermolecular bonds. Preferable conformations are defined via ethylamine chain, resulting in six different conformations. Molecular Structure īiochemically, the indoleamine molecule derives from the amino acid tryptophan, via the (rate-limiting) hydroxylation of the 5 position on the ring (forming the intermediate 5-hydroxytryptophan), and then decarboxylation to produce serotonin. Its widespread presence in many seeds and fruits may serve to stimulate the digestive tract into expelling the seeds. Serotonin is produced by pathogenic amoebae, causing diarrhea in the human gut. Serotonin's presence in insect venoms and plant spines serves to cause pain, which is a side-effect of serotonin injection. Several classes of antidepressants, such as selective serotonin reuptake inhibitors (SSRIs) and serotonin–norepinephrine reuptake inhibitors (SNRIs), interfere with the normal reabsorption of serotonin after it is done with the transmission of the signal, therefore augmenting the neurotransmitter levels in the synapses.īesides mammals, serotonin is found in all bilateral animals including worms and insects, as well as in fungi and in plants. Serotonin is metabolized mainly to 5-hydroxyindoleacetic acid, chiefly by the liver. There are various serotonin receptors.īiochemically, the indoleamine molecule derives from the amino acid tryptophan. Serotonin is also a growth factor for some types of cells, which may give it a role in wound healing. In normal physiologic states, vasodilation occurs through the serotonin mediated release of nitric oxide from endothelial cells, and the inhibition of release of norepinephrine from adrenergic nerves. The vasoconstrictive property is mostly seen in pathologic states affecting the endothelium – such as atherosclerosis or chronic hypertension. In high concentrations, serotonin acts as a vasoconstrictor by contracting endothelial smooth muscle directly or by potentiating the effects of other vasoconstrictors (e.g. When the platelets bind to a clot, they release serotonin, where it can serve as a vasoconstrictor or a vasodilator while regulating hemostasis and blood clotting. There, it is actively taken up by blood platelets, which store it. Serotonin secreted from the enterochromaffin cells eventually finds its way out of tissues into the blood. The remainder is synthesized in serotonergic neurons of the CNS, where it has various functions, including the regulation of mood, appetite, and sleep. 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. About 8% is found in platelets and 1–2% in the CNS. Additionally, it is stored in blood platelets and is released during agitation and vasoconstriction, where it then acts as an agonist to other platelets. Serotonin is also produced in the central nervous system (CNS), specifically in the brainstem's raphe nuclei, the skin's Merkel cells, pulmonary neuroendocrine cells and the tongue's taste receptor cells. ![]() Approximately 90% of the serotonin the human body produces is in the gastrointestinal tract's enterochromaffin cells, where it regulates intestinal movements. ![]() Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vasoconstriction. Serotonin ( / ˌ s ɛr ə ˈ t oʊ n ɪ n, ˌ s ɪər ə-/) or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. ![]()
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