Klein R L, Mascia M P, Whiting P J, Harris R A
Department of Pharmacology, University of Colorado Health Sciences Center, Denver 80262, USA.
Alcohol Clin Exp Res. 1995 Oct;19(5):1338-44. doi: 10.1111/j.1530-0277.1995.tb01622.x.
Effects of chronic ethanol exposure on GABAA receptors may contribute to tolerance and dependence to alcohol. Ethanol treatment of mice and rats can produce alterations of GABAA receptor binding, function, and subunit mRNA and protein levels. We treated a cell line (PA3 cells) that stably expresses GABAA receptors chronically with ethanol. Expression of bovine alpha 1, beta 1, and gamma 2L GABAA receptor subunits genes in these cells is controlled by a dexamethasone-sensitive promoter, and this provides an excellent system to study the regulation by chronic ethanol treatment of receptors with a defined subunit composition. The actions of the GABA agonist muscimol on receptor function (36Cl- uptake) were not affected by 100 mM ethanol treatment for 4 days, but the actions of flunitrazepam (1 microM) were decreased in cells treated with ethanol. The functional coupling between benzodiazepine and GABA sites on the receptors was affected by chronic ethanol treatment in a manner consistent with results from mice. Ethanol treatments (50 or 100 mM) for 4 days did not affect the affinity (Kd) or receptor density (Bmax) of [3H]flunitrazepam binding, or the levels of alpha 1 subunit mRNA, or alpha 1 or beta 1 subunit proteins. These results demonstrate that the regulation of the stably expressed GABAA receptors by chronic ethanol, in the absence of neuronal receptor gene promoters, is posttranscriptional and likely posttranslational.
长期乙醇暴露对γ-氨基丁酸A型（GABAA）受体的影响可能导致对酒精的耐受性和依赖性。对小鼠和大鼠进行乙醇处理可引起GABAA受体结合、功能以及亚基mRNA和蛋白质水平的改变。我们用乙醇对稳定表达GABAA受体的细胞系（PA3细胞）进行长期处理。这些细胞中牛α1、β1和γ2L GABAA受体亚基基因的表达受地塞米松敏感启动子的控制，这为研究慢性乙醇处理对具有特定亚基组成的受体的调节提供了一个极佳的系统。γ-氨基丁酸（GABA）激动剂蝇蕈醇对受体功能（36Cl-摄取）的作用不受100 mM乙醇处理4天的影响，但在乙醇处理的细胞中，氟硝西泮（1 μM）的作用减弱。受体上苯二氮䓬和GABA位点之间的功能偶联受到慢性乙醇处理的影响，其方式与小鼠实验结果一致。4天的乙醇处理（50或100 mM）不影响[3H]氟硝西泮结合的亲和力（Kd）或受体密度（Bmax），也不影响α1亚基mRNA水平或α1或β1亚基蛋白的水平。这些结果表明，在没有神经元受体基因启动子的情况下，慢性乙醇对稳定表达的GABAA受体的调节是转录后和可能的翻译后调节。
