Serotonin
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.
In the central nervous system, serotonin is believed to play an important role in the regulation of mood, sleep, emesis (vomiting), sexuality and appetite. Low levels of Serotonin have been associated with several disorders, notably depression, migraine, bipolar disorder and anxiety.
Isolated and named in 1948 by Maurice M. Rapport, the name "serotonin" is something of a misnomer and reflects the circumstances of the compound's discovery.
It was initially identified as a vasoconstrictor substance in blood serum — hence serotonin, a serum agent affecting vascular tone.
This agent was later chemically identified as 5-hydroxytryptamine (5-HT) by Rapport, and, as the broad range of physiological roles were elucidated, 5-HT became the preferred name in the pharmacological field.
Serotonin is found extensively in the human gastrointestinal tract (about 90% [1]), as well as in the blood stream.
In the body, serotonin is synthesized from the amino acid tryptophan by a short metabolic pathway consisting of two enzymes — TPH(1,2) and DDC. TPH1 reaction controls the flux through the pathway. The gut secretes over 95% of the body's serotonin[1].
Serotonin taken orally does not pass into the serotonergic pathways of the central nervous system because it does not cross the blood-brain barrier. However, the amino acid tryptophan and its metabolite 5-hydroxytryptophan (5-HTP), from which serotonin is synthesized, can and do cross the blood-brain barrier. These agents are available as dietary supplements and may be effective serotonergic agents
More here
http://en.wikipedia.org/wiki/SeratoninAnyone seen my sanity? I know I left it around here somewhere...
I don't know, maybe it's the black on it, it almost looks medical to me. (Edit: Like a prescription, d'oh, maybe I should slow down and read the whole post next time. 
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