Ethanol Activation of Protein Kinase A Regulates GABAA a1 Receptor Function and Trafficking in Cultured Cerebral Cortical Neurons

Ethanol exposure produces alterations in GABAergic signaling that are associated with dependence and withdrawal. Previously, we demonstrated that ethanol-induced protein kinase C (PKC) g signaling selectively contributes to changes in GABAA a1 synaptic receptor activity and surface expression. Here, we demonstrate that protein kinase A (PKA) exerts opposing effects on GABAA receptor adaptations during brief ethanol exposure. Cerebral cortical neurons from day 0–1 rat pups were tested after 18 days in culture. Receptor trafficking was assessed by Western blot analysis, and functional changes were measured using whole-cell patch-clamp recordings of evoked and miniature inhibitory postsynaptic current (mIPSC) responses. Onehour ethanol exposure increasedmembrane-associated PKC and PKA, but steady-state GABAA a1 subunit levels were maintained. Activation of PKA by Sp-adenosine 39,59-cyclic monophosphothioate triethylamine alone increased GABAA a1 subunit surface expression and zolpidempotentiation of GABA responses, whereas coexposure of ethanol with the PKA inhibitor Rp-adenosine 39,59-cyclic monophosphothioate triethylamine decreased a1 subunit expression and zolpidem responses. Exposure to the PKC inhibitor calphostin-C with ethanol mimicked the effect of direct PKA activation. The effects of PKA modulation on mIPSC decay t were consistent with its effects on GABA currents evoked in the presence of zolpidem. Overall, the results suggest that PKA acts in opposition to PKC on a1-containing GABAA receptors, mediating the GABAergic effects of ethanol exposure, and may provide an important target for the treatment of alcohol dependence/withdrawal.