IN VITRO RELEASE OF LUTEINIZING HORMONE-RELEASING HORMONE (LHRH) FROM RAT MEDIOBASAL HYPOTHALAMUS: EFFECTS OF POTASSIUM, CALCIUM AND DOPAMINE.

Abstract

A suitable preparation to study the effect of dopamine (DA) on in vitro LHRH secretion is presented. Enzymatic degradation of LHRH in the incubation medium is completely inhibited by bacitracin (2 .times. 10-5 M). A high K concentration (56 mM) induces an increase in LHRH release from entire pieces of mediobasal hypothalamus (MBH), but not from a synaptosomal pellet; this release is inhibited when Ca is omitted. The depolarization-induced LHRH release in vitro is independent of the initial amount of the peptide present in the MBH. In contrast, DA (10-6 M) is not effective in vitro on MBH from ovariectomized rats but induces a fast release of LHRH from MBH of normal male and estradiol-pretreated ovariectomized rats. The preparation appears to be of great interest in investigating amine-steroid-LHRH interactions at the cellular level.