Luteinizing hormone release induced by noradrenaline after administration of drugs that increase hypothalamic GABA levels.

Recent evidence shows that GABA exhibits inhibitory actions on LH release in rats. Its mechanism of action remains unknown. In this study, the LH discharge evoked by noradrenaline (NA), one of the neuroactive substances that regulate LHRH neurons, in rats pretreated with drugs that augment brain GABA levels, was examined. Gamma-acetylenic- and gamma-vinyl-GABA were injected into the 3rd ventricle of ovariectomized-estrogen-progesterone-treated rats. Under these conditions, animals exhibited a marked LH discharge after NA administration as seen in the controls receiving saline solution as pretreatment. It is concluded that LHRH neurons retain their ability to respond to NA when hypothalamic GABA levels are increased.