[Development of animal models for the chronobiotics of melatonin analogs].

Melatonin is a neurohormone secreted by the pineal gland (or epiphysis). It is secreted only during the night whether in man or in diurnal or nocturnal animals. Melatonin secretion is regulated by light, which inhibits or synthesizes it. By a 'feedback' mechanism, melatonin can regulate the suprachiasmatic nuclei which function like internal clocks at the level of melatonin receptors. Specific melatonin agonists are active in different animal models representative of sleep disturbances due to alterations of circadian rhythms.