Friday, November 28, 2008

sarah's fireside chats: melatonin edition

Not to be confused with melanin or melanotan.

"Melatonin, also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring hormone found in most animals, including humans, and some other living organisms, including algae. Circulating levels vary in a daily cycle, and melatonin is important in the regulation of the circadian rhythms of several biological functions. Many biological effects of melatonin are produced through activation of melatonin receptors, while others are due to its role as a pervasive and powerful antioxidant with a particular role in the protection of nuclear and mitochondrial DNA."

"Production of melatonin by the pineal gland is inhibited by light and permitted by darkness. For this reason melatonin has been called "the hormone of darkness" and its onset each evening is called the Dim-Light Melatonin Onset (DLMO). Secretion of melatonin as well as its level in the blood, peaks in the middle of the night, and gradually falls during the second half of the night, with normal variations in timing according to an individual's chronotype."

"Melatonin levels at night are reduced to 50% by exposure to a low-level incandescent bulb for only 39 minutes, and it has been shown that women with the brightest bathrooms have an increased risk for breast cancer.
Reduced melatonin production has been proposed as a likely factor in the significantly higher cancer rates in night workers, and the effect of modern lighting practice, including light pollution, on endogenous melatonin has been proposed as a contributory factor to the larger overall incidence of some cancers in the developed world."

"Many animals use the variation in duration and quantity of melatonin production each day as a seasonal clock. In animals and in some conditions also in humans the profile of melatonin synthesis and secretion is affected by the variable duration of night in summer as compared to winter. The change in duration of secretion thus serves as a biological signal for the organisation of daylength-dependent (photoperiodic) seasonal functions such as reproduction, behaviour, coat growth and camouflage colouring in seasonal animals. In seasonal breeders which do not have long gestation periods, and which mate during longer daylight hours, the melatonin signal controls the seasonal variation in their sexual physiology, and similar physiological effects can be induced by exogenous melatonin in animals including mynah birds and hamsters. Melatonin is also related to the mechanism by which some amphibians and reptiles change the color of their skin and, indeed, it was in this connection the substance first was discovered
"In animal models, melatonin has been demonstrated to prevent the damage to DNA by some carcinogens, stopping the mechanism by which they cause cancer. It also has been found to be effective in protecting against brain injury caused by ROS release in experimental hypoxic brain damage in newborn rats. Melatonin's antioxidant activity may reduce damage caused by some types of Parkinson's disease, may play a role in preventing cardiac arrhythmia and may increase longevity; it has been shown to increase the average life span of mice by 20% in some studies."

"Many supplemental melatonin users have reported an increase in vivid dreaming. Extremely high doses of melatonin (50mg) dramatically increased REM sleep time and dream activity in both narcoleptics and those without narcolepsy. However, one factor that may influence this perception is that many over-the-counter melatonin tablets also include Vitamin B6 (pyroxidine), which is also known to be capable of producing vivid dreams.
Many psychoactive drugs, such as LSD, increase melatonin synthesis. It has been suggested that nonpolar (lipid-soluble) indolic hallucinogenic drugs emulate melatonin activity in the awakened state and that both act on the same areas of the brain. It has been suggested that psychotropic drugs be readmitted in the field of scientific inquiry and therapy. If so, melatonin may be prioritized for research in this reemerging field of psychiatry."

"Melatonin has been studied for the treatment of alzheimer's disease, cancer, immune disorders, cardiovascular diseases, depression, seasonal affective disorder (SAD), circadian rhythm sleep disorders and sexual dysfunction. Studies by Alfred J. Lewy at Oregon Health & Science University and other researchers have found that it may ameliorate circadian misalignment and SAD. Basic research indicates that melatonin may play a significant role in modulating the effects of drugs of abuse such as cocaine."


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