Prolactin Response to Morphine and Stress in Brattleboro Hetero- and Homozygous Rats

Abstract

The posterior pituitary has been shown to participate in the regulation of prolactin (rPRL) secretion in the rat. This effect is considered to be due to inhibitory action of dopamine reaching the adenopituitary via short (hypophyseal portal vessels (Ben-Jonathan and Peters 1982 and others). In addition, rPRL secretion could be affected by neuro­ hypophyseal hormones. Experiments of Shin (1982) indicated that physiological doses of vasopressin could elevate circulating rPRL levels in normal male rats as well as the rPRL secretion from trans­ planted pituitaries. From these findings this author suggests a direct prolactin releasing factor like activity of vasopressin in rats. There­ fore the question arose whether endogenous vasopressin is one of the factors inducing rPRL secretion in response to exogenous stimuli acting via the prolactin releasing pathways. We have studied the stimulatory effect of morphine and endogenous opioids induced by stress on rPRL release in Brattleboro homozygous (DI rats) and heterozygous (non-DI rats) rats.