Ethanol Regulation of Neuronal Nicotinic Receptor Expression in Reward Circuitry

描述（由申请人提供）：神经元尼古丁乙酰胆碱受体是由内源性神经递质乙酰胆碱（ACh）以及烟草中高度上瘾的成分尼古丁激活的配体门控阳离子通道。神经元nachr在多巴胺能中皮质边缘通路（“奖励”通路）中的表达对于尼古丁的奖励特性是必要的，但它们也与酒精的强化作用有关。像所有滥用药物一样，乙醇会增加伏隔核中多巴胺（DA）的释放，这与强化有关。阻断nAChRs可阻止DA释放，抑制运动刺激和乙醇自我给药。酒精如何与nachr相互作用以促进强化？有趣的是，乙醇被认为可以增加VTA中乙酰胆碱的释放，从而增加胆能神经元中表达的nachr的活性。此外，乙醇已被证明直接增强或抑制nAChR对乙酰胆碱的反应，这取决于受体的亚基组成。综上所述，这些数据表明，长期暴露于乙醇中可能会长期激活nachr。由于已知尼古丁对nAChR的慢性激活可以调节其表达，我们假设乙醇也有可能调节nAChR的表达。在Aim 1中，我们将利用实时定量RT-PCR分析急性或慢性乙醇暴露后小鼠脑关键区域中所有12个神经元nAChR基因mRNA表达的变化。定量免疫印迹也将用于测量酒精暴露时nAChR蛋白表达的变化。Aim 2将采用生物物理方法来测量中脑关键区域急性或慢性乙醇暴露时nAChR功能的变化。我们预计，这项研究的结果不仅将确定奖赏回路中由乙醇调节的nAChR亚型，而且还将为戒酒治疗提供潜在的分子靶点。

DESCRIPTION (provided by applicant): Neuronal nicotinic acetylcholine receptors are ligand-gated cation channels activated by the endogenous neurotransmitter, acetylcholine (ACh), as well as the highly addictive component of tobacco, nicotine. Expression of neuronal nAChRs in the dopaminergic mesocorticolimbic pathways (the 'reward' pathways) are necessary for nicotine's rewarding properties, but they have also been implicated in the reinforcing effects of alcohol. Ethanol, like all drugs of abuse, increases dopamine (DA) release in nucleus accumbens which is associated with reinforcement. Blocking nAChRs prevents DA release, and inhibits both locomotor stimulation and ethanol self-administration. How may alcohol interact with nAChRs to contribute to reinforcement? Interestingly, ethanol has been proposed to increase ACh release in the VTA thereby increasing the activity of nAChRs expressed in DAergic neurons. In addition, ethanol has been shown to directly either potentiate or inhibit the nAChR response to ACh depending on the subunit composition of the receptor. Together, these data suggest that chronic exposure to ethanol may chronically activate nAChRs. Since it is known that chronic activation of nAChRs by nicotine modulates expression, we hypothesize that ethanol has the potential to regulate nAChR expression, as well. In Aim 1, we will utilize quantitative real time RT-PCR to analyze mRNA expression changes in all 12 neuronal nAChR genes in key mouse brain areas implicated in addiction after acute or chronic ethanol exposure. Quantitative immunoblotting will also be used to measure changes in nAChR protein expression with alcohol exposure. A biophysical approach will be utilized in Aim 2 to measure changes in nAChR function with acute or chronic ethanol exposure in key midbrain areas. We anticipate that the results from this study will not only identify nAChR subtypes regulated by ethanol in reward circuitry, but also lead to a potential molecular target for alcohol cessation therapeutics. PUBLIC HEALTH RELEVANCE: Alcoholism is the third largest cause of preventable mortality in the world. The goal of the proposed project is to understand how alcohol may regulate expression and function of neuronal nicotinic acetylcholine receptors, key proteins critically involved in the addictive properties of both alcohol and nicotine. The insights gained from this project should help elucidate the molecular mechanism underlying alcoholism, as well as identify molecular targets for alcohol cessation therapeutics.