Molecular Mechanisms of Ethanol Reinforcement

乙醇增强的分子机制

• 批准号: 6988739
• 负责人: Clyde W Hodge
• 金额: $ 31.7万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-05 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6988739
• 关键词: alcoholism /alcohol abuse; behavior test; behavioral /social science research tag; biological signal transduction; blood tests; cAMP response element binding protein; ethanol; glutamate receptor; immunocytochemistry; laboratory rat; light microscopy; molecular biology; nucleus accumbens; operant conditionings; protein kinase C; psychological reinforcement; substance abuse related behavior

DESCRIPTION (provided by applicant): The primary goal of this application is to characterize the involvement of metabotropic glutamate receptor subtype-5 receptors (mGluR5) in alcohol's reinforcing effects. Preliminary evidence indicates that chronic alcohol drinking selectively increases mGluR5 mRNA expression in the nucleus accumbens (NAcb) of rats, which is consistent with chronic receptor inhibition by alcohol in a brain region that is fundamental to development of addiction. Experiments in Aim 1 of this project will more fully characterize the involvement of mGluR5 in alcohol reinforcement. These studies will determine if operant alcohol self-administration alters mGluR5 protein expression and if mGluR5 receptor activity functionally regulates ethanol reinforcement in rats. Other preliminary data indicate that microinjection of an mGluR5 antagonist in the NAcb decreases the reinforcing effects of ethanol. Studies in Aim 2 will extend this observation by determining the functional significance of mGluR5 receptor activity in limbic brain regions that express mGluR5. Experiments will determine the effects of site-specific infusion of an mGluR5 antagonist in the ventral tegmental area (VTA), NAcb (core and shell), or medial prefrontal cortex (mPFC) on ethanol reinforced responding. These studies will determine if mGluR5 regulation of alcohol reinforcement is brain-region specific. Evidence indicates that ethanol inhibits mGluR5 function in vitro through a PKC-dependent mechanism. Similarly, our preliminary data indicate that mGluR5 blockade decreases ethanol self-administration in wildtype mice but has no effect in mice carrying a null mutation for PKC-epsilon. Thus, specific Aim 3 will characterize a potential cell- signaling based mechanism in mGluR5 regulation of alcohol reinforcement. Using PKC-epsilon knockout and wildtype mice, experiments will determine if mGluR5 blockade decreases ethanol reinforcement in a PKC-epsilon dependent manner. These studies will examine the effects of mGluR antagonists on alcohol and sucrose reinforced responding, and on ethanol-induced changes in locomotor activity to determine behavioral specificity. Finally, chronic ethanol exposure alters numerous molecular events in the brain including the gene transcription factor cyclic AMP- responsive element binding protein (CREB), which has been implicated in addictive behavior. Activation of mGluR5 increases p-CREB levels via a PKC dependent mechanism, whereas chronic ethanol drinking decreases p-CREB levels in the NAcb. Since ethanol is known to inhibit mGluR5 activity through a PKC-dependent mechanism, these findings suggest that self-administered ethanol may decrease p-CREB through an mGluR5/PKC (possibly PKCepsilon) dependent mechanism. Experiments in Aim 4 will determine if ethanol-induced changes in mGluR5 and p-CREB expression are dependent on PKCe, and the extent to which this is modulated by a history of chronic operant ethanol self-administration. Another study will determine if ethanol inhibits mGluR5-mediated changes in p-CREB in a PKCepsilon dependent manner. These studies, examine the functional linkage between mGluR5 and PKCepsilon in the mediation of chronic ethanol effects on transcriptional regulation, which has implications for adaptive changes in addiction. These findings will aid development of pharmacotherapeutics to treat problems associated with alcoholism.

描述（由申请人提供）：本申请的主要目标是表征代谢型谷氨酸受体亚型 5 受体 (mGluR5) 在酒精增强作用中的作用。初步证据表明，长期饮酒会选择性增加大鼠伏隔核 (NAcb) 中 mGluR5 mRNA 的表达，这与酒精对大脑区域中受体的慢性抑制一致，而酒精对成瘾的发展至关重要。该项目目标 1 的实验将更全面地表征 mGluR5 在酒精强化中的作用。这些研究将确定操作性酒精自我给药是否会改变 mGluR5 蛋白表达，以及 mGluR5 受体活性是否在功能上调节大鼠的乙醇强化。其他初步数据表明，在 NAcb 中显微注射 mGluR5 拮抗剂会降低乙醇的增强作用。目标 2 中的研究将通过确定表达 mGluR5 的边缘脑区域中 mGluR5 受体活性的功能意义来扩展这一观察结果。实验将确定腹侧被盖区 (VTA)、NAcb（核心和外壳）或内侧前额皮质 (mPFC) 中特定位点注射 mGluR5 拮抗剂对乙醇增强反应的影响。这些研究将确定 mGluR5 对酒精强化的调节是否具有大脑区域特异性。有证据表明乙醇通过 PKC 依赖性机制在体外抑制 mGluR5 功能。同样，我们的初步数据表明，mGluR5 阻断减少了野生型小鼠的乙醇自我给药，但对携带 PKC-ε 无效突变的小鼠没有影响。因此，特定的目标 3 将表征 mGluR5 调节酒精强化的潜在细胞信号转导机制。使用 PKC-ε 敲除和野生型小鼠，实验将确定 mGluR5 阻断是否以 PKC-ε 依赖性方式减少乙醇强化。这些研究将检查 mGluR 拮抗剂对酒精和蔗糖强化反应的影响，以及对乙醇诱导的运动活动变化的影响，以确定行为特异性。最后，长期接触乙醇会改变大脑中的许多分子事件，包括基因转录因子环AMP反应元件结合蛋白（CREB），它与成瘾行为有关。 mGluR5 的激活通过 PKC 依赖性机制增加 p-CREB ​​水平，而长期饮酒会降低 NAcb 中的 p-CREB ​​水平。由于已知乙醇通过 PKC 依赖性机制抑制 mGluR5 活性，因此这些发现表明，自我施用乙醇可能通过 mGluR5/PKC（可能是 PKCepsilon）依赖性机制降低 p-CREB。目标 4 中的实验将确定乙醇诱导的 mGluR5 和 p-CREB ​​表达变化是否依赖于 PKCe，以及这种变化在多大程度上受到长期操作性乙醇自我给药史的调节。另一项研究将确定乙醇是否以 PKCepsilon 依赖性方式抑制 mGluR5 介导的 p-CREB ​​变化。这些研究检查了 mGluR5 和 PKCepsilon 在介导慢性乙醇对转录调节的影响中的功能联系，这对成瘾的适应性变化具有影响。这些发现将有助于开发治疗酗酒相关问题的药物疗法。