ABSTRACT
Melatonin (5-methoxy-N-acetyltryptamine) is a major hormone produced by the pinealgland. Presence of melatonin in the pineal gland was first reported in 1958 by Lerneret al.75 Since this discovery it was clearly demonstrated that melatonin plays crucial role in the regulation daily and seasonal rhythms, pigment metabolism, immune response, reproductive function and other vitally important physiological processes in all photoperiodic species.50 Melatonin synthesis depends on the duration of the day and the intensity of the light, reflecting annual photoperiodic changes. Being an endocrine messenger, melatonin quantitatively transfers a photic signal to others tissues, expressing its own receptors, deliver thus timing information to the organism.102
