Chronic Ethanol IncreasesN-Methyl-d-Aspartate-Stimulated Nitric Oxide Formation but Not Receptor Density in Cultured Cortical Neurons
- 1Department of Pharmacology, Louisiana State University Medical Center, Shreveport, Louisiana 71130-3932 (L.J.C., G.S., D.N.),2Department of Physiology, University of Florida College of Medicine, Gainesville, Florida 32610 (C.S.), and 3Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 (F.T.C.)
Abstract
The effects of prolonged ethanol exposure on excitatory amino acid receptor stimulated nitric oxide (NO) formation were examined in primary rat cortical neuronal cultures. Chronic ethanol (4 days, 100 mm) potentiatedN-methyl-d-aspartate (NMDA)-stimulated NO formation as determined by measuring the conversion of [3H]arginine to [3H]citrulline. In contrast, chronic ethanol had no effect on NO formation stimulated by kainate, α-amino-3-hydroxy-5-methyl-4-isoxalonepropionic acid, or the calcium ionophore ionomycin. Potassium chloride-stimulated NO formation was also enhanced by chronic ethanol treatment, but this effect was not seen in the presence of the ionotropic glutamate receptor antagonists MK-801 and 6-cyano-7-nitroquinoxaline-2,3-dione. Immunoblot analysis of expression of NR1, NR2A, and NR2B receptor subunits showed no difference between control and chronic ethanol-treated cultures. In support of this apparent lack of change in receptor density, there was no difference in the specific binding of125I-MK-801 between control and chronic ethanol-treated groups. These results demonstrate that prolonged ethanol exposure selectively enhanced NMDA receptor-stimulated NO formation, which may play an important role in alcohol dependence, withdrawal, and alcohol-associated brain damage. These results also suggest that chronic ethanol-induced increases in NMDA receptor function may not be due to a simple increase in the number of NMDA receptors or change in NMDA receptor subunit composition but may instead reflect more complicated and subtle changes.
Footnotes
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Send reprint requests to: Dr. L. Judson Chandler, Department of Pharmacology, Louisiana State University Medical Center, 1501 Kings Highway, Shreveport, LA 71130-3932.
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This work was supported by National Institute on Alcohol Abuse and Alcoholism Grants AA00127 and AA06069, National Institutes of Health Grant NS19441, and a grant from the Alcoholic Beverage Medical Research Foundation.
- Abbreviations:
- AMPA
- α-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid
- CNQX
- 6-cyano-7-nitroquinoxaline-2,3-dione
- DMEM
- Dulbecco’s modified Eagle’s medium
- HEPES
- 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- NMDA
- N-methyl-d-aspartate
- NO
- nitric oxide
- NOS
- nitric oxide synthase
- NR
- N-methyl-d-aspartate receptor subunit
- PBST
- phosphate-buffered saline/Tween 20
- SDS
- sodium dodecyl sulfate
- PDHS
- plasma-derived horse serum
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- Received June 24, 1996.
- Accepted January 29, 1997.
- The American Society for Pharmacology and Experimental Therapeutics
