ABSTRACT
Melatonin (5-methoxy-N-acetyltryptamine) has been discovered in the pineal gland by Aaron Lerner, a dermatologist from Yale University, more than 50 years ago [1]. This indoleamine is produced from the amino acid l-tryptophan in a reaction controlled by speci£c enzymes, two of them are arylalkylamino-N-acetyl-serotonin-transferase (AA-NAT) and hydroxyindolo-O-methyltransferase (HIOMT) [2]. Secretion of this pineal product is directed by the suprachiasmatic nucleus in response to light/dark cycles, with a peak at night and reduction during the day [3]. Melatonin is best known as a regulator of seasonal and circadian rhythms, but the physiological role of this substance has been unclear for many years [4].
