Localization in the brain of the inhibition by GABA of luteinizing hormone release that follows orchidectomy in rats.

The possible participation of GABA (gamma-aminobutyric acid) in the enhanced release of luteinizing hormone that follows orchidectomy was examined. The GABA-transaminase inhibitor, gamma vinyl GABA, injected stereotaxically into the locus ceruleus area blocked the postcastration rise of luteinizing hormone in plasma. In contrast, this response developed normally when the drug was administered either to the medial or the dorsal preoptic area and to the mediobasal hypothalamus. The present preliminary results suggest that the increase of GABA at synaptic sites affects luteinizing hormone release in castrated male rats through an action on the noradrenergic cell bodies of the locus ceruleus system.