GABA control of LHRH release is dependent on the steroid milieu

The effect of GABA in controlling luteinizing hormone releasing hormone (LHRH) release from isolated hypothalamic fragments containing the mediobasal hypothalamus, suprachiasmatic nucleus, and the preoptic area (MBH-SCN-POA) was tested under different hormonal conditions with an in vitro superfusion method. GABA significantly decreased LHRH release under conditions of low, chronic levels of estradiol (E2) treatment but had no effect on tissue obtained from animals in proestrus. This suggests that the inhibitory effect of GABA is only manifested during certain stages of the estrous cycle characterized by negative feedback and low E2.