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Lege Artis Medicinae

JULY 27, 2009

[Melatonin, sleep and the circadian rhythm: theoretical considerations and their chronopharmacological applications ]

BÓDIZS Róbert

[The predictive homeostasis of living organisms is an anticipatory adaptation to rhythmical environmental changes. A good example for this is the circadian rhythm preparing the organism for the alternation of day and night. The circadian rhythm of melatonin production anticipates the timing and duration of nocturnal sleep of human subjects. It also induces a sleep-like stimulusprocessing mode of the brain and - in case of adequate environmental circumstances - a soporific and in part, a sleep-inducing effect. Specificities of melatonin effects on sleep are the reduction of slow-wave EEG activity, as well as the increase in seep EEG spindling and REM sleep time. Like other substances with hypnotic properties, melatonin decreases core body temperature, but has also a strong chronobiotic effect that is expressed as rapid and strong phase shifts of the circadian rhythm, depending on the time of day of melatonin administration. Because light acutely suppresses melatonin production, adequately timed light exposition, containing also low wavelength components, together with exogenous melatonin, could be useful in treating jet-lag syndrome and other circadian rhythm disorders.]