Research related to the pineal gland has advanced rapidly in the last three decades since the discovery of its most important hormone, melatonin. This indoleamine has been shown to have a large variety of effects in the organism; the bulk of these actions were initially thought to relate the pineal gland to the reproductive and endocrine systems. It is now apparent, however, that the physiologic interactions of the pineal and its hormones far transcend its control of endocrine function. One field of pineal research that has developed rapidly within the last 5 years has been the demonstration...