ABSTRACT
Melatonin (N-acetyl-5-methoxytryptamine) is a molecule known for more than half a century as a mediator of biological and physiological rhythms in mammals. It was initially known to be produced exclusively in the pineal gland, but melatonin synthesis has been found in different sites of the organism, and the major sources of extrapineal melatonin are the central nervous system and immune system [1,2]. It is characterized by a wide spectrum of properties, including those involved in sleep and circadian rhythms [3], lipid metabolism [4], immune defense [5,6], tumor inhibition [7], drug detoxi£cation [8], bone physiology [9], and free radical scavenger and antioxidant activities [10]. Some of these actions are receptor-mediated [4,7], while others are receptor-independent [11].
