Serotonin
Serotonin (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesised in serotonergic neurons in the central nervous system and enterochromaffin cells in the gastrointestinal tract.
Serotonin is believed to play an important part of the biochemistry of depression, bipolar disorder and anxiety. It is also believed to be influential on sexuality and appetite.
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) 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, or gut, as well as in the blood stream.
In our body, serotonin is synthesized from the amino
acid tryptophan
by various enzymes as shown in the reaction below.
Serotonin taken orally does not pass into the serotonergic pathways of the central nervous system (CNS). This is due to the blood-brain barrier preventing serotonin in the blood stream from affecting serotonin levels in the brain. However, the amino acid tryptophan and its metabolite 5-hydroxytryptophan, from which serotonin is synthesized, are capable of crossing the blood-brain barrier. These agents are available as dietary supplements and may be effective serotonergic agents, though their efficacy is questionable.