Regulation of NMDA Receptor Localization by Ethanol

已显示慢性乙醇暴露增加小鼠和大鼠脑中NMDA受体配体结合和受体亚单位蛋白质水平。海马NMDA受体的增加被认为与乙醇戒断性癫痫发作的发生和对谷氨酸诱导的兴奋性毒性的易感性增加有关，也可能导致认知改变，并可能导致乙醇强化和对乙醇的“渴望”的变化。与NMDA受体相反，很少有人注意到乙醇诱导的非NMDA（AMPA）谷氨酸受体的改变，这也可能导致乙醇暴露和戒断后的长期认知变化。虽然海马NMDA受体的配体结合的变化的时间过程平行的时间过程中的乙醇戒断发作的发生和消散，长期的适应性变化，NMDA和/或非NMDA谷氨酸受体可能不仅涉及受体亚单位蛋白水平的增加，但也改变了细胞表面表达和/或突触定位的受体。这些性质的变化，具有重要的功能后果，可能发生在受体合成增加的存在或不存在。我们建议评估慢性乙醇治疗后产生身体依赖和戒断的NMDA和AMPA受体的突触靶向适应。这种受体变化可能是持久的，并有助于认知缺陷以及神经毒性易感性的长期增加。使用生物化学和免疫组织化学技术，在目标1中，我们将研究适应谷氨酸受体突触定位和细胞表面表达的C57 BL/6小鼠，长期摄入乙醇的液体饮食，并经历了撤退。NMDA受体功能和亚单位蛋白水平的增加也被发现在培养的小鼠和大鼠神经元已长期暴露于乙醇，因此在目的2中，我们将研究谷氨酸受体定位在乙醇处理/撤回海马神经元，以确定乙醇在体外系统和体内的影响之间的平行关系。然后，这些研究将允许在目标3中详细研究导致慢性乙醇暴露导致NMDA和/或AMPA受体特性变化的分子机制。拟议的研究超越了以前的现象学观察，以确定乙醇暴露如何导致影响突触可塑性的适应，并可能有助于与成瘾相关的CNS变化。了解这些机制可以提供新的治疗方法，以改善慢性乙醇摄入和戒断的神经后果。

Chronic ethanol exposure has been shown to increase NMDA receptor ligand binding and the levels of receptor subunit proteins in mouse and rat brain. The increase in hippocampal NMDA receptors has been suggested to be related to the occurrence of ethanol withdrawal seizures and to increased susceptibility to glutamate-induced excitotoxicity, and could also result in altered cognition and could contribute to changes in ethanol reinforcement and "craving" for ethanol. In contrast to NMDA receptors, little attention has been given to ethanol-induced alterations in non-NMDA (AMPA) glutamate receptors, which could also contribute to long-term cognitive changes following ethanol exposure and withdrawal. Although the time course of changes in ligand binding to the hippocampal NMDA receptor parallels the time course for the occurrence and dissipation of ethanol withdrawal seizures, long-term adaptive changes in NMDA and/or non-NMDA glutamate receptors may involve not only increases in receptor subunit protein levels, but also altered cell surface expression and/or synaptic localization of the receptors. Changes in these properties, which have important functional consequences, could occur either in the absence or presence of increased receptor synthesis. We propose to assess adaptations in synaptic targeting of NMDA and AMPA receptors following chronic ethanol treatment that produces physical dependence and withdrawal. Such receptor changes may be long-lasting, and contribute to cognitive deficits as well as prolonged increases in susceptibility to neurotoxicity. Using both biochemical and immunohistochemical techniques, in Aim 1 we will investigate adaptations in glutamate receptor synaptic localization and cell surface expression in hippocampus of C57BL/6 mice that have ingested ethanol chronically in a liquid diet, and undergone withdrawal. Increases in NMDA receptor function and subunit protein levels have also been found in cultured mouse and rat neurons that have been exposed chronically to ethanol, and thus in Aim 2 we will investigate glutamate receptor localization in ethanol-treated/withdrawn hippocampal neurons, to determine parallels between effects of ethanol in this in vitro system and in vivo. These studies will then allow a detailed investigation in Aim 3 of the molecular mechanisms that lead to changes in NMDA and/or AMPA receptor properties as a result of chronic ethanol exposure. The proposed studies go beyond previous phenomenological observations to determine how ethanol exposure results in adaptations that affect synaptic plasticity and may contribute to the CNS changes associated with addiction. Understanding these mechanisms can provide novel therapeutic approaches to ameliorating the neuronal consequences of chronic ethanol ingestion and withdrawal.