Role of NR2B Subunit in Glutamate Signaling and Anxiety during Ethanol Withdrawal

项目摘要/摘要：酒精中毒是一种慢性复发性精神障碍。随着酒精使用向依赖转变，动机驱动力从最初受到正面强化(酒精带来的愉悦效果)的影响转变为后来对负面强化(酒精戒断/负面影响)的依赖。在戒毒过程中，调节依赖受试者复发的一种行为是焦虑。因此，了解戒酒过程中导致焦虑的机制对于酒精中毒的治疗至关重要。杏仁延伸核(终纹床核；BNST和杏仁中央核；CEA)是调节焦虑和应激反应的区域。这些核团已被证明调节对焦虑性刺激和应激诱导的药物依赖复发的反应，因此对了解酒精依赖至关重要。延伸的杏仁核中存在的一个神经递质系统特别容易受到乙醇的影响，那就是谷氨酸。多条证据表明，药物相关剂量的急性乙醇注射选择性地抑制谷氨酸通过NMDA受体(NMDAR)的传递。此外，乙醇似乎对含有NR2B(也称为GluN2B)亚单位的NMDAR具有更高的选择性。虽然急性乙醇后NMDAR功能受到抑制，但更多的慢性乙醇给药要么促进要么抑制谷氨酸传递，这取决于评估的区域。一些研究已经证明，乙醇对NMDAR的这些影响发生在延伸的杏仁核区域(BNST和CEA)。在CEA中，急性乙醇抑制NMDAR，而慢性乙醇处理增强了这种抑制。此外，NR2B拮抗剂能够阻断乙醇对急性和慢性乙醇处理的抑制。在BNST中，急性乙醇抑制NMDAR反应，慢性乙醇暴露以NR2B相关的方式增强NMDAR反应。由于延伸的杏仁核的这些区域对焦虑的调节至关重要，这些区域中谷氨酸传递的中断可能有助于酒精戒断诱导的焦虑的产生。在评估NR2B在乙醇效应中的具体作用时，主要的困难是NMDAR的复杂药理学。这些问题可以通过使用有条件的和病毒敲除(KO)的NR2B来规避。这项建议将评估NR2B在急性乙醇后抑制NMDAR功能和慢性治疗后NMDAR功能增强/抑制方面的需求(NR2B有条件和病毒KO)(目标1)。此外，这项工作将评估NR2B亚单位，条件KO和病毒KO，在基础和戒断诱导的焦虑由慢性酒精暴露(目标2)。

Project Summary/Abstract: Alcoholism is known to be a chronic relapsing disorder. As alcohol use transitions to dependence, there is a shift in the motivational drive from being initially influenced by positive reinforcement (pleasurable effects from ethanol) to later reliance on negative reinforcement (withdrawal/negative affect from ethanol). One behavior that modulates relapse in dependent subjects during withdrawal is anxiety. Therefore, understanding the mechanisms that contribute to anxiety during withdrawal is critically important to the treatment of alcoholism. A region that is particularly involved in the modulation of anxiety and stress is the extended amygdala (bed nucleus of the stria terminalis; BNST and central nucleus of the amygdala; CeA).These nuclei have been shown to modulate responses to anxiogenic stimuli and stress- induced relapse to drug taking and, therefore, critical to the understanding of ethanol dependence. One neurotransmitter system present in the extended amygdala that is particularly susceptible to the effects of ethanol is glutamate. Multiple lines of evidence have illustrated that acute ethanol administration at pharmacologically relevant doses selectively inhibits glutamate transmission through the NMDA receptor (NMDAR). Further, ethanol also seems to be selectivity more sensitive to NMDARs that contain NR2B (also referred to as the GluN2B) subunit. While there is an inhibition of NMDAR function following acute ethanol, more chronic ethanol administrations either enhance or inhibit glutamate transmission depending on the region evaluated. Several studies have demonstrated that these effects of ethanol on NMDARs occur in regions of the extended amygdala (BNST and CeA). In the CeA, acute ethanol inhibited NMDARs, while chronic ethanol treatment enhanced this inhibition. Further, a NR2B antagonist was able to block this ethanol induced inhibition from acute and chronic ethanol treatment. In the BNST, acute ethanol inhibits NMDAR responses and chronic ethanol exposure enhances their function in an NR2B related manner. Since these regions of the extended amygdala are critical for the modulation of anxiety, it is possible the disrupted glutamate transmission in these regions could contribute to the production of ethanol withdrawal-induced anxiety. The major complication in evaluating the specific role of NR2B in ethanol's effects is the complex pharmacology of NMDARs. These problems can be circumvented with the use of both a conditional and viral knock-out (KO) of NR2B. This proposal will evaluate the requirement of NR2B (with conditional and viral KO of NR2B) in the inhibition of NMDAR function following acute ethanol and the enhancement/inhibition of NMDAR function following chronic treatment (Aim 1). Further, this work will assess the role of the NR2B subunit, with conditional and viral KOs, in basal and withdrawal induced anxiety from chronic ethanol exposure (Aim 2).