Melatonin, or 5-methoxy-N-acetyltryptamine, is a hormone produced by pinealocytes in
the pineal gland, located in the brain, but also in the retina and GI tract. It a
derivative of the amino acid tryptophan.
Melatonin produced in the pineal gland acts as an endocrine hormone since it is
released into the blood. On the other hand, melatonine produced by the retina and the
GI tract is considered a paracrine hormone.
Melatonin helps regulate sleep-wake or circadian rhythms. Normally, production of
melatonin by the pineal gland is stimulated by darkness and inhibited by light. Nobel
Prize laureate Julius Axelrod performed many of the seminal experiments elucidating
the role of melatonin and the pineal gland in circadian rhythms. Beta blockers
decrease nocturnal melatonin release.
Melatonin is synthesized by various plants such as rice and ingested melatonin was
shown to be capable of reaching and binding to melatonin binding sites in the brain
of mammals [1]
(http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=77731
97&dopt=Abstract).
In recent times, melatonin has become available as a drug and a dietary supplement.
It appears to have some use against insomnia and jet lag. It has been studied for the
treatment of cancer, immune disorders, cardiovascular diseases, depression, seasonal
affective disorder, and sexual dysfunction; no apparent benefit in these has been
found.
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