Dopamine: A Prolactin-Inhibiting Hormone*

Abstract

DOPAMINE (DA) is an interesting and versatile compound. In the central nervous system (CNS) it is involved with the control of fine movements and mental processes. Its association with disorders such as Parkinsonism and schizophrenia is well recognized. In the hypothalamo-hypophysial axis, DA is the primary physiological inhibitor of PRL secretion. Currently, this catecholamine represents the only nonpeptidergic hypothalamic agent with a well defined hypophysiotropic function. By virtue of its dual role as a neurotransmitter and a hormone, DA provides perhaps the best example of neuroendocrine interactions. It also possesses a more universal property. In all hormonal systems studied thus far, whether at the hypothalamic, posterior pituitary, or anterior pituitary level, DA functions as an inhibitor. Perhaps the common denominator to these diverse cells is the presence of D2 DA receptors, which are negatively linked to the adenylate cyclase system.