Protein kinase C epsilon mediates up-regulation of N-type calcium channelsby ethanol

Brief exposure to ethanol inhibits L-type and N-type voltage-gated calcium channels in neural cells. Although chronic ethanol exposure up-regulates th e density and function of L-type channels via a protein kinase C (PKC) delt a-dependent mechanism, the effect of prolonged ethanol exposure on N-type c hannels is not known. Using PC12 cells, we found that exposure to 25 to 150 mM ethanol for 0 to 8 days produced a time- and concentration-dependent in crease in the density of binding sites for the N-type channel antagonist I- 125-omega-conotoxin GVIA. This was associated with an increase in omega-con otoxin GVIA-sensitive, depolarization-evoked rises in [Ca2+](i). Increases in I-125-omega-conotoxin GVIA binding also were observed in the frontal cor tex and the hippocampus, but not in the thalamus of mice exposed to ethanol vapor for 3 days. In PC12 cells, increases in I-125-omega-conotoxin GVIA b inding were blocked by the PKC inhibitor bisindolylmaleimide I and by expre ssion of a selective peptide inhibitor of PKC epsilon. Expression of a sele ctive inhibitor of PKC delta did not alter ethanol-induced increases in I-1 25-omega-conotoxin GVIA binding. These findings indicate that PKC epsilon m ediates upregulation of N-type channels by ethanol. Because N-type channels modulate calcium-dependent neurotransmitter release, these findings sugges t a mechanism that may contribute to neuronal hyperexcitability observed du ring alcohol withdrawal.