Dr. Reiter plans to study the mechanisms involved in the regulation of pineal melatonin production during the long nights (short days) in the rat and the hamster. The relative contribution of the different neurotransmitter systems as well as different components of the same system may vary from species to species and also from long day to short day conditions. Investigation of mechanisms underlying sustained synthesis and secretion of melatonin will significantly enhance the understanding of melatonin's role in mammalian physiology.//