RESUMO
Our perception of pineal gland function has attained new dimensions during the last decade. The gland is active throughout the life of an individual and secretes melatonin, the major pineal hormone, and many indoles and polypeptides. The secretion of pineal gland is regulated not only by sympathetic nerve fibers but by other central pinealopetal projections also. Many neurotransmitter-receptor sites have been identified recently in the pineal gland. The gland plays an established role in controlling reproduction and is involved in the control of sexual maturation. It has a major influence on the circadian organization of vertebrates including human beings. The hormone melatonin has a potential therapeutic valve in treating disorders that are associated with biological rhythm disturbances like sleep disorders, "jet lag" phenomena and affective disorders. The gland is actively involved in the mechanisms controlling sleep-wakefulness cycle and human mood disorders. It actively participates in the neuroendocrine mechanism controlling stress and acts even as an oncostatic gland. The pineal gland may be considered an "equilibrating-tranquilizing gland" contributing to longevity.