Abstract Circadian (∼ 24-hour) timing systems pervade all kingdoms of life and temporally
optimize behavior and physiology in humans. Relatively recent changes to our …

In humans, an adaptable internal biological system generates circadian rhythms that
maintain synchronicity of behavior and physiology with the changing demands of the 24-h …

Caffeine is the most widely consumed psychoactive substance in the world. It is readily
available in coffee and other foods and beverages, and is used to mitigate sleepiness …

I. Introduction U NTIL 35 yr ago, most scientists did not take research on the pineal gland
seriously. The decade beginning in 1956, however, provided several discoveries that laid …

Three centuries ago, the French philosopher René Descartes described the pineal gland as
“the seat of the soul,” but it was not until the late 1950s that melatonin, the principal …

The hormone melatonin (5-methoxy-N-acetyltryptamine) is synthesized primarily in the
pineal gland and retina, and in several peripheral tissues and organs. In the circulation, the …

Levels of numerous hormones vary across the day and night. Such fluctuations are not only
attributable to changes in sleep/wakefulness and other behaviors but also to a circadian …

The paper briefly reviews the data which shows that the circadian production and secretion
of melatonin by the pineal gland can impart both daily, ie, clock, and seasonal, ie, calendar …

Melatonin, dubbed the hormone of darkness, is known to regulate a wide variety of
physiological processes in mammals. This review describes well-defined functional …

The pineal hormone melatonin regulates seasonal reproductive function and modulates
circadian rhythms in mammals. We now report the cloning and characterization of a high …