Mechanisms of altered prolactin secretion due to the administration of interleukin-1 beta into the brain ventricles of the rat.

Abstract

The ability of the intracerebroventricular (icv) injection of interleukin-1 beta (IL-1 beta) to alter plasma prolactin (PRL) levels in rats remains controversial, with reports of increases, decreases, or no changes in secretory rate. These discordant results may reflect, at least in part, the use of different doses of cytokines, as well as a gender specificity in the response of the brain circuits that control PRL release. In a first series of experiments, we investigated the effect of one acute icv injection of IL-1 beta to alter PRL secretion in intact male and female rats. Using this paradigm, we also determined the potential modulating role of secretagogues reportedly released by IL-1 beta, such as dopamine, corticosterone and progesterone. A second series of experiments involved the long-term (3-5 days) i.c.v. infusion of IL-1 beta to identify the influence of gender on the pattern of PRL release. The acute icv injection of IL-1 beta (5-50 ng) to intact adult males or females caused comparable and significant (p < 0.01) decreases in plasma PRL levels 1-5.5 h after treatment. At the 8 h time point PRL secretion started to increase in females exposed to the cytokine, while PRL values of males were comparable in vehicle- and IL-1-injected rats. In intact males, blockade of pituitary dopamine receptors with domperidone (3.5 mg/kg) did not reverse the inhibitory effect of the immune protein. In either gender, blockade of IL-1-induced corticosterone and adrenal progesterone release with CRF antibodies was also without effect on PRL secretion.(ABSTRACT TRUNCATED AT 250 WORDS)