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疾病。当酒精使用转变为依赖时，动机驱动从最初受到正强化（乙醇带来的愉悦效果）的影响转变为后来对负强化（乙醇的戒断/负面影响）的依赖。在戒断期间调节依赖对象复发的一种行为是焦虑。因此，了解戒断期间导致焦虑的机制对酒精中毒的治疗至关重要。一个特别参与焦虑和压力调节的区域是延伸的杏仁核（终纹床核；杏仁核的BNST和中央核；CeA）。这些核已被证明可以调节对焦虑性刺激和应激诱导的药物复发的反应，因此对理解乙醇依赖至关重要。在扩展的杏仁核中存在的一种神经递质系统特别容易受到乙醇的影响，这就是谷氨酸。多种证据表明，在药理学上相关剂量的急性乙醇给药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）亚基的NMDARs选择性更敏感。虽然急性乙醇对NMDAR功能有抑制作用，但根据所评估的区域，更长期的乙醇治疗可以增强或抑制谷氨酸的传递。一些研究表明，乙醇对NMDARs的这些影响发生在扩展的杏仁核区域（BNST和CeA）。在CeA中，急性乙醇能抑制NMDARs，而慢性乙醇能增强这种抑制作用。此外，NR2B拮抗剂能够阻断急性和慢性乙醇治疗中乙醇诱导的这种抑制作用。在BNST中，急性乙醇抑制NMDAR反应，而慢性乙醇暴露以NR2B相关的方式增强其功能。由于扩展杏仁核的这些区域对焦虑的调节至关重要，因此这些区域的谷氨酸传递中断可能有助于产生乙醇戒断诱导的焦虑。评估NR2B在乙醇作用中的具体作用的主要并发症是NMDARs的复杂药理学。这些问题可以通过NR2B的条件和病毒敲除（KO）来规避。该提案将评估NR2B（条件性和病毒性NR2B KO）在急性乙醇治疗后抑制NMDAR功能和慢性治疗后增强/抑制NMDAR功能中的要求（Aim 1）。此外，这项工作将评估NR2B亚基在慢性乙醇暴露的基础焦虑和戒断性焦虑中的作用，包括条件性和病毒性KOs（目的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).