The long-term goal of this project is to examine the biochemical, endocrinological and toxicological effects of drugs which influence catecholaminergic neurons in the central nervous system. Particular attention will be directed toward the actions of drugs which influence tuberoinfundibular and tuberohypophyseal dopaminergic neuronal systems. The characteristics of the neurons in these minor dopaminergic systems will be compared with those in the major nigrostriatal and mesolimbic (meso-telencephalic) dopaminergic systems. Efforts will be made to determine what functions each of these neuronal systems regulate and, in turn, what regulates the activity of these neurons.