The mammalian brain contains anatomically distinct dopaminergic neuronal systems that subserve a variety of functions which include maintaining postural reflexes, modulating basic psychic processes, and controlling the secretion of hormones from the pituitary. In turn, these various dopaminergic neuronal systems are regulated by different mechanisms that are appropriate for the functions that they control. This is illustrated by comparing the responses to endocrinological and pharmacological manipulations of the nigrostriatal dopaminergic neuronal system that is involved with sensorimotor integration and the tuberoinfundibular dopaminergic neuronal system that tonically inhibits the release of prolactin.