Effect of ethanol on mouse cerebral cortical beta-adrenergic receptors

Low concentrations of ethanol (10-100 mM), added to assays in vitro, altered agonist (isoproterenol) binding to mouse cerebral cortical beta-adrenergic receptors in a reversible manner. Ethanol decreased the affinity of the high affinity form of the receptor for isoproterenol but had no effect on the affinity of the low affinity form of the receptor, the proportion of high and low affinity forms of the receptor, the total number of agonist-binding sites, or antagonist binding. The selective effect of ethanol on the properties of the high affinity agonist-binding site suggested that ethanol alters the characteristics of the complex of the receptor and Gs, the guanine nucleotide-binding protein. In cerebral cortical membranes of mice that had ingested ethanol chronically, isoproterenol binding data were best fit by a one-site model, even in the absence of guanine nucleotides. This change, when considered together with previously reported changes in adenylate cyclase activity, is reminiscent of heterologous desensitization of the beta-adrenergic receptor. Thus, both acute and chronic ethanol administration may produce changes in adrenergic function in brain.