Inhibition of luteinizing hormone secretion in ovariectomized ewes during the breeding season by γ-aminobutyric acid (GABA) is mediated by GABA-A receptors, but not GABA-B receptors

Abstract

We have investigated the effects of agonists and antagonists to γ-aminobutyric acid-A (GABA-A) and GABA-B receptors microinjected (1 μl) into the preoptic area (POA) on LH in ovariectomized (OVX) ewes with or without estrogen (E) treatment during the breeding season. Guide tubes were placed into the preoptic area of OVX ewes using lateral ventriculograms for localization of the target area. Doses of 10 μg of the GABA agonists muscimol (GABA-A) and baclofen (GABA-B) or the GABA antagonists bicuculline (GABA-A) and phaclofen (GABA-B) were injected into the POA of tame conscious animals. Jugular venous blood was collected at 10-min intervals for 3 h, the injection of GABA drug or vehicle was gi..