Effect of Gamma‐Aminobutyric Acid on the Release of Prolactin, Luteinizing Hormone and Follicle Stimulating Hormone in Spayed Rats

The effect of Gamma-Aminobutyric Acid (GABA) on the release of Prolactin (PRL), Luteinizing Hormone (LH), and Follicle Stimulating Hormone (FSH) in spayed rats was studied. Adult female rats of the Wistar strain were ovariectomized 30 days prior to the experiments and various doses of GABA and/or picrotoxin (PCT) were injected into the third ventricle under Nembutal anesthesia. A dose of 10-8 mole GABA produced a marked decrease in plasma PRL levels. On the other hand, the addition of 10-8 mole PCT to 10-8 mole GABA antagonized the inhibitory effect of GABA, whereby plasma PRL levels returned to pretreatment values. Plasma LH levels increased significantly after intraventricular administration of 10-7 mole of GABA. FSH concentrations remained unchanged after the same treatment. Intraventricular injection of GABA interfered with central nervous system (CNS) function in the periventricular region and activated hypothalamic nerve cells. Participation of the hypothalamic inhibitory interneurons in inhibition of PRL release and the LH secretion stimulatory mechanism were discussed.