Abstract

At least three substances have been reported to be present in the hypothalamus that can inhibit prolactin release, namely a PIF, catecholamines and acetylcholine. At least four substances have been reported to be present in the hypothalamus that can stimulate prolactin release, namely PRF, TRH, serotonin and prostaglandins. Neither the existence of a distinctive PIF or PRF in the hypothalamus can be considered as definitely established. The predominant action of the mammalian hypothalamus on prolactin release is inhibitory under most conditions, and is stimulatory in avian species. In addition to control by the hypothalamus, several hormones and drugs can act directly on the pituitary to alter prolactin release. The interrelationships of these agents within and without the hypothalamus on prolactin secretion are complex, and there are many questions about their mode of action. Studies on the regulation of prolactin secretion have resulted in development of many methods for either increasing or decreasing release of this important hormone, and thereby have provided opportunities for influencing lactation, growth of mammary and pituitary tumors and other tissues responsive to prolactin.