Effects of Chronic Ethanol Treatment on the β-Adrenergic Receptor-Coupled Adenylate Cyclase System of Mouse Cerebral Cortex |
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Authors: | Toshikazu Saito John M Lee Paula L Hoffman Boris Tabakoff |
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Institution: | Alcohol and Drug Abuse Research and Training Program, Department of Physiology and Biophysics, University of Illinois at Chicago, Health Sciences Center, Chicago, Illinois, U.S.A.;National Institute on Alcohol Abuse and Alcoholism, Laboratory of Physiologic and Pharmacologic Studies, National Institutes of Health, Bethesda, Maryland, U.S.A. |
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Abstract: | Chronic ingestion of ethanol, which produced tolerance and physical dependence, resulted in altered function of the cerebral cortical beta-adrenergic receptor-coupled adenylate cyclase system in mice. Although there was no change in basal adenylate cyclase activity, or in the activity of the digitonin-solubilized catalytic unit, stimulation of adenylate cyclase activity by the nonhydrolyzable guanine nucleotide analog guanylylimidodiphosphate Gpp(NH)p] was reduced in brains of ethanol-fed animals. Ethanol added in vitro increased adenylate cyclase activity, and this enhancement, in the presence of Gpp(NH)p, was also reduced in cortical membranes of ethanol-fed mice. Furthermore, the maximal response to isoproterenol was decreased, and the EC50 for isoproterenol stimulation of adenylate cyclase activity was increased in ethanol-fed animals. The results are consistent with a qualitative or quantitative defect in the function of the stimulatory guanine nucleotide-binding protein (Ns), as well as in the beta-adrenergic receptor, after chronic ethanol exposure. In part, these changes appear to be similar to those that occur during heterologous desensitization of various receptor systems, and may be associated with dependence on or tolerance to ethanol. |
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Keywords: | Ethanol tolerance Ethanol physical dependence Adenylate cyclase Cerebral cortex Ns function β-Adrener-gic receptor |
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