Chronopharmacological actions of the pineal gland.

In all mammalian species studied to date, the pineal gland shows a pronounced circadian rhythm with high activity at night and very low activity in daytime, as reflected in the output of its hormone, melatonin. The pineal is one of the few organs which can synthesize melatonin and, under normal circumstances, is virtually the only source of circulating melatonin. Pineal activity is tightly controlled by the light/dark cycle, in such a manner …