Devaud Leslie L, Alele Paul
Department of Pharmaceutical Sciences, Idaho State University, Pocatello, Idaho 83209-8334, USA.
Alcohol Clin Exp Res. 2004 Jun;28(6):957-65. doi: 10.1097/01.alc.0000128225.83916.40.
Investigations have shown that chronic ethanol exposure results in selective alterations in levels of gamma-aminobutyric acid (GABA)A and NMDA receptor subunits. We previously reported significant sex differences in these chronic ethanol-induced adaptations. Because we have more recently found important sex differences in timing for the development of and recovery from ethanol dependence, we wanted to ascertain whether there were associations between overt expression of withdrawal and neuroadaptations at the level of GABAA and NMDA receptors.
Western blot analysis was used to assay protein levels for several GABAA and NMDA receptor subunits in rat cerebral cortex and hippocampus by using subunit-selective antibodies. Rats were fed 6% ethanol in a liquid diet with pair-fed controls. Feeding, harvesting of tissue, and Western blot experiments were all conducted while maintaining the paired design. Tissue was harvested after 3 days of ethanol exposure, 9 days of ethanol exposure, or 3 days of ethanol withdrawal after 14 days of liquid diet administration.
We again found sex-, subunit-, and brain region-selective effects of ethanol administration and withdrawal for GABAA and NMDA receptors. There was a strong association between increased GABAA receptor alpha4 subunit levels and previously determined withdrawal-induced changes in seizure susceptibility, highlighted by the sex differences in ethanol exposure length required to cause withdrawal signs. In addition, results obtained after 9 days of ethanol administration were in general agreement with previous findings after 14 days of ethanol administration.
These data further support the suggestion that alterations in subunit assembly of GABAA and NMDA receptors may have some mechanistic role in neuroadaptations underlying ethanol dependence and withdrawal. Furthermore, significant sex differences in these adaptations suggest that multiple types of adaptations may be elicited, depending on innate differences in the actions/effects of ethanol.
研究表明，长期乙醇暴露会导致γ-氨基丁酸（GABA）A和NMDA受体亚基水平发生选择性改变。我们之前报道了这些慢性乙醇诱导的适应性变化存在显著的性别差异。由于我们最近发现乙醇依赖的发生和恢复时间存在重要的性别差异，因此我们想确定戒断的明显表现与GABAA和NMDA受体水平的神经适应性之间是否存在关联。
通过使用亚基选择性抗体，采用蛋白质印迹分析来检测大鼠大脑皮层和海马体中几种GABAA和NMDA受体亚基的蛋白质水平。给大鼠喂食含6%乙醇的液体饲料，并设置配对喂食对照组。在维持配对设计的同时进行喂食、组织采集和蛋白质印迹实验。在给予液体饲料14天后，分别在乙醇暴露3天、9天后或乙醇戒断3天后采集组织。
我们再次发现乙醇给药和戒断对GABAA和NMDA受体存在性别、亚基和脑区选择性效应。GABAA受体α4亚基水平升高与先前确定的戒断诱导的癫痫易感性变化之间存在强烈关联，导致戒断体征所需的乙醇暴露时间的性别差异突出了这一点。此外，乙醇给药9天后获得的结果与之前乙醇给药14天后的发现总体一致。
这些数据进一步支持以下观点，即GABAA和NMDA受体亚基组装的改变可能在乙醇依赖和戒断的神经适应性中具有某种机制作用。此外，这些适应性变化中存在显著的性别差异表明，根据乙醇作用/效应的先天差异，可能会引发多种类型的适应性变化。
