title: Light, melatonin and the sleep-wake cycle.
abstract: Blood levels of the pineal hormone melatonin are high at night and low during the day. Its secretion is regulated by a rhythm-generating system located in the suprachiasmatic nucleus of the hypothalamus, which is in turn regulated by light. Melatonin is regulated not only by that circadian oscillator but acts as a darkness signal, providing feedback to the oscillator. Melatonin has both a soporific effect and an ability to entrain the sleep-wake rhythm. It also has a major role in regulating the body temperature rhythm. Melatonin rhythms are altered in a variety of circadian rhythm disorders. Melatonin treatment has been reported to be effective in treatment of disorders such as jet lag and delayed sleep phase syndrome.
authors: Clarke Institute of Psychiatry, Toronto, Ontario.
authors: G M
authors: GM
authors: Brown
mesh_terms: D001831:Body Temperature; D002940:Circadian Rhythm; D006801:Humans; D007031:Hypothalamus / Q000502:physiology; D008027:Light; D008550:Melatonin / Q000097:blood / Q000378:metabolism*; D010870:Pineal Gland / Q000502:physiology; D012890:Sleep; D014851:Wakefulness
chemical_list: D008550:Melatonin