Vol. 57, Issue 1, 53-58, January 2000

Protein Kinase C  Mediates Up-Regulation of N-Type Calcium Channels by Ethanol

Thomas McMahon, Reid Andersen, Pamela Metten, John C. Crabbe, and Robert O. Messing

Department of Neurology, Ernest Gallo Clinic & Research Center (T.M., R.A., R.O.M.) and Graduate Programs in Neuroscience and Biomedical Sciences (R.O.M.), University of California, San Francisco; and the Portland Alcohol Research Center (P.M., J.C.C.), Department of Veterans Affairs Medical Center and Oregon Health Sciences University, Portland, Oregon

Brief exposure to ethanol inhibits L-type and N-type voltage-gated calcium channels in neural cells. Although chronic ethanol exposure up-regulates the density and function of L-type channels via a protein kinase C (PKC) -dependent mechanism, the effect of prolonged ethanol exposure on N-type channels 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 increase in the density of binding sites for the N-type channel antagonist ¹²⁵I--conotoxin GVIA. This was associated with an increase in -conotoxin GVIA-sensitive, depolarization-evoked rises in [Ca²⁺]_i. Increases in ¹²⁵I--conotoxin GVIA binding also were observed in the frontal cortex and the hippocampus, but not in the thalamus of mice exposed to ethanol vapor for 3 days. In PC12 cells, increases in ¹²⁵I--conotoxin GVIA binding were blocked by the PKC inhibitor bisindolylmaleimide I and by expression of a selective peptide inhibitor of PKC. Expression of a selective inhibitor of PKC did not alter ethanol-induced increases in ¹²⁵I--conotoxin GVIA binding. These findings indicate that PKC mediates up-regulation of N-type channels by ethanol. Because N-type channels modulate calcium-dependent neurotransmitter release, these findings suggest a mechanism that may contribute to neuronal hyperexcitability observed during alcohol withdrawal.