Progesterone enhances inhibitory responses of cerebellar Purkinje cells mediated by the GABAA receptor subtype

Abstract

Previous studies from this laboratory have indicated that the sex steroid progesterone (P) is able to augment inhibitory responses of cerebellar Purkinje cells to the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in the urethane anesthetized adult female rat. Because both GABAA and GABAB receptors are localized in this CNS area, agonist/antagonists for these receptors were utilized in the present evaluation in order to delineate the specific receptor subtype involved in P-GABA interactions. Systemically administered P was found to augment GABA-mediated inhibition by an average of 80%. Concomitant application of the GABAA blocker, bicuculline, greatly reduced this modulatory effect of the steroid. In contrast, P administration had no effect on baclofen-induced inhibition. These data suggest that P effects on GABA physiology are mediated predominantly at the GABAA receptor. © 1989.