Effect of neutransmitters on in vitro release of luteinizing-hormone-releasing hormone from the mediobasal hypothalamus of male rats.

Effects of neurotransmitters on in vitro release of lutein-hormone-releasing hormone (LHRH) from fragments of hypothalamic tissue were investigated. Neither acetylcholine (ACh) or histamine (HA) at concentrations of 10(-7) and 10(-5) M, or GABA at 10(-7) to 5 x 10(-5) M affected LHRH release from mediobasal hypothalamic (MBH) fragments or the organum vasculosum of the laminae terminalis (OVLT). In contrast, serotonin (10(-7) and 10(-5) M) significantly inhibited the release of LHRH from the MBH but not from the OVLT. This response to serotonin (5-HT) is no longer observed in presence of methiothepin, a 5-HT receptor antagonist. The present results confirm in vivo data suggesting that the inhibitory effect of serotonin on the release of LHRH from median eminence involves a direct action on neurosecretory nerve-endings.