Development of animal models for demonstrating the activity of chronobiotics or melatonin analogues

Melatonin is a neurohormone secreted by the pineal gland (or epiphysis). It is secreted only during the night whether in man of in diurnal or nocturna l animals. Melatonin secretion is regulated tn light, which inhibits or syn thetizes it. By a 'feedback' mechanism, melatonin can regulate the suprachi asmatic nuclei which function like internal clocks at the level of melatoni n receptors. Specific melatonin agonists are active in different animal mod els representative of sleep disturbances due to alterations of circadian rh ythms.