Oxytocin Regulates Neurosteroid Modulation of GABAAReceptors in Supraoptic Nucleus around Parturition

In this study, we investigate how neurosteroid sensitivity of GABAAreceptors (GABAARs) is regulated. We examined this issue in neurons of the supraoptic nucleus (SON) of the rat and found that, during parturition, the GABAARs become insensitive to the neurosteroid allopregnanolone attributable to a shift in the balance between the activities of endogenous Ser/Thr phosphatase and PKC. In particular, a constitutive endogenous tone of oxytocin within the SON after parturition suppressed neurosteroid sensitivity of GABAARs via activation of PKC. Vice versa before parturition, during late pregnancy, application of exogenous oxytocin brings the GABAARs from a neurosteroid-sensitive mode toward a …