Ethanol alters GABAA receptor trafficking and function through activation of protein kinases, and these changes may underlie ethanol dependence and withdrawal. In the present study, we utilized subsynaptic fraction techniques and patch clamp electrophysiology to investigate the biochemical and functional effects of protein kinase A (PKA) and PKC activation by ethanol on synaptic GABAA α4 receptors, a key target of ethanol-induced changes. Rat cerebral cortical neurons were grown for 18 days in vitro and exposed to ethanol and/or kinase modulators for 4 h, a paradigm that recapitulates GABAergic changes found after chronic ethanol in vivo. PKA activation by forskolin or rolipram during ethanol exposure prevented increases in P2 fraction α4 subunit abundance, while inhibiting PKA had no effect. Similarly, in the synaptic fraction activation of PKA by rolipram in the presence of ethanol prevented the increase in synaptic α4 subunit abundance while inhibiting PKA in the presence of ethanol was ineffective. Conversely, PKC inhibition in the presence of ethanol prevented the ethanol-induced increases in synaptic α4 subunit abundance. Finally, we found that either activating PKA or inhibiting PKC in the presence of ethanol prevented the ethanol-induced decrease in GABA mIPSC decay τ1, while inhibiting PKA had no effect. We conclude that PKA and PKC have opposing effects in the regulation of synaptic α4 receptors, with PKA activation negatively modulating, and PKC activation positively modulating, synaptic α4 subunit abundance and function. These results suggest potential targets for restoring normal GABAergic functioning in the treatment of alcohol use disorders.
- The American Society for Pharmacology and Experimental Therapeutics