Abstract
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) δ-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-ω-conotoxin GVIA. This was associated with an increase in ω-conotoxin GVIA-sensitive, depolarization-evoked rises in [Ca2+]i. Increases in125I-ω-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 in125I-ω-conotoxin GVIA binding were blocked by the PKC inhibitor bisindolylmaleimide I and by expression of a selective peptide inhibitor of PKCε. Expression of a selective inhibitor of PKCδ did not alter ethanol-induced increases in125I-ω-conotoxin GVIA binding. These findings indicate that PKCε 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.
Footnotes
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Send reprint requests to: Robert O. Messing, M.D., 5858 Horton St., Suite 200, Emeryville, CA 94608. E-mail:romes{at}itsa.ucsf.edu
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This work was supported by grants from the National Institute on Alcohol Abuse and Alcoholism (to R.O.M.), the Department of Veterans Affairs (to J.C.C.), and the Alcoholic Beverage Medical Research Foundation (to R.O.M).
- Abbreviations:
- DHP
- dihydropyridine
- PKC
- protein kinase C
- Received August 2, 1999.
- Accepted October 6, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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