Action Serotonin Functions

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Serotonin

Chemical Nature/Structure:

Serotonin (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesized in serotonergic neurons in the central nervous system (CNS) and enterochromaffin cells in the gastrointestinal tract. The neurons in the brain that release serotonin are found in small dense collections of neurons called Raphe Nuclei. The Raphe Nuclei are found in the medulla, pons and midbrain which are all located at the top of the spinal cord. Serotonergic neurons have axons which project to many different parts of the brain, therefore serotonin affects (Rosling, Claire, 2004). In the body, serotonin is synthesized from the amino acid tryptophan by the activity of the enzymes Tryptophan hydroxylase (TPH) and Amino acid decarboxylase (DDC) (Dolnak, Douglas R. DO, 2006). The enzyme tryptophan hydroxylase adds a hydroxyl group to tryptophan's benzene ring at position 5, creating 5-hydroxytryptophan. Another enzyme, amino acid decarboxylase, then removes a carboxyl group from 5-hydroxytryptophan, forming 5-hydroxytryptamine which is more commonly known as serotonin. The average adult human possesses only 5 to 10 mg of serotonin, 90 % of which is in the intestine and the rest in blood platelets and the brain (Rosling, Claire, 2004). Stimuli necessary for secretion

Serotonin is known to cause vasoconstriction and cellular proliferation in pulmonary arteries. Levels of serotonin are elevated in the plasma of patients with primary pulmonary arterial hypertension (Hippisley-Cox, Julia; Katherine Fielding, and Mike Pringle, 1998). Serotonin is also secreted in excess by carcinoid tumours. Some foods such as bananas, pineapples and walnuts contain serotonin and can increase the excretion of 5-HIAA (Maroteaux, Luc and Canan G. Nebigil, 2003). Studies have shown that serotonin levels are increased with increased exercise and the production of serotonin is increased for some days after the activity (Rosling, Claire, 2004). Serotonin levels...
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