Alcohol and mesolimbic glutamatergic transmissions

描述(申请人提供)：在美国，酗酒是一个严重的健康问题。我们的长期目标是阐明酒精成瘾的机制，这是开发有效治疗方法的必要前提。具体的假设是，急性乙醇通过激活多巴胺D1受体(D1R)增加谷氨酸的释放。谷氨酸能传递的增加反过来调节了奖赏通路中的多巴胺能细胞的活动，从而在酒精成瘾的过程中发挥了重要作用。我们基于以下观察结果提出这一假说：a)临床相关浓度的乙醇(10-80 mM)可增加AMPA受体介导的兴奋性突触后电流(EPSCs)的幅度。此外，乙醇降低了诱发的EPSCs的成对脉冲促进作用，并增加了自发EPSCs的频率，但不增加幅度。此外，乙醇增加了大鼠中脑片和体内腹侧被盖区(VTA)的细胞外谷氨酸水平；以及b)乙醇的作用可被D1R激动剂或多巴胺再摄取抑制剂模拟，并被D1R拮抗剂或利血平耗尽多巴胺储备所阻断。这一假说将通过电生理学和药理学技术的组合在大鼠或小鼠的VTA中进行测试。这包括测量VTA和伏隔核、脑片和/或体内的细胞外谷氨酸和多巴胺水平。其具体目的是确定：1)乙醇对谷氨酸能传递给VTA多巴胺神经元的影响。我们将比较AMPA受体介导的EPSCs和细胞外谷氨酸和多巴胺在无乙醇和有乙醇存在的情况下的水平。2)突触前D1Rs在乙醇增加谷氨酸能传递给VTA多巴胺神经元中的作用。我们将比较乙醇对EPSCs的影响，以及在没有和存在D1R激动剂或拮抗剂的情况下对细胞外谷氨酸水平的影响。3)乙醇促进谷氨酸释放对VTA多巴胺神经元输出的功能影响。我们将确定谷氨酸拮抗剂是否：1)减弱乙醇对VTA DA神经元兴奋性的影响，2)当拮抗剂注入VTA时，阻断全身乙醇增加伏隔核多巴胺释放的能力。与公共健康相关这些研究的结果将阐明一种新的机制，这是乙醇对大脑奖励途径作用的重要组成部分。更好地了解酒精成瘾的细胞机制将有助于酒精中毒的治疗和预防。

DESCRIPTION (provided by applicant): Alcoholism in the United States is a serious health concern. Our long-term goal is to elucidate the mechanisms underlying alcohol addiction, a necessary prerequisite to the development of effective therapy. The specific hypothesis is that acute ethanol increases glutamate release via activation of dopamine D1 receptors (D1R). The increased glutamatergic transmission in turn modulates dopaminergic cell activity in the reward pathway and thus plays a significant role in the processes involved in alcohol addiction. We base this hypothesis on the following observations: a) clinically relevant concentrations of ethanol (10-80 mM) increase the amplitude of evoked excitatory postsynaptic currents (EPSCs) mediated by AMPA receptors. In addition, ethanol reduces paired-pulse facilitation of evoked EPSCs and increased the frequency but not the amplitude of spontaneous EPSCs. Furthermore, ethanol increases extracellular glutamate levels in the ventral tegmental area (VTA) in midbrain slices and in vivo in rats; and b) the effects of ethanol are mimicked by a D1R agonist or a dopamine reuptake inhibitor, and they are blocked by a D1R antagonist or by depleting dopamine stores with reserpine. This hypothesis will be tested in the VTA of rats or mice by a combination of electrophysiological and pharmacological techniques. This includes measurements of extracellular glutamate and dopamine levels in both the VTA and the nucleus accumbens, in brain slices and/or in vivo. The Specific Aims are to determine: 1) The effects of ethanol on glutamatergic transmission to VTA dopamine neurons. We will compare AMPA receptor-mediated EPSCs and extracellular glutamate and dopamine levels in the absence and presence of ethanol. 2) The role of presynaptic D1Rs in the ethanol-induced increase in glutamatergic transmission to VTA dopamine neurons. We will compare the effects of ethanol on EPSCs and on extracellular glutamate levels in the absence and presence of a D1R agonist or antagonist. 3) The functional consequences of ethanol-mediated facilitation of glutamate release on the output of VTA dopamine neurons. We will determine whether glutamate antagonists: 1) attenuate the effects of ethanol on the excitability of VTA DA neurons, and 2) block the ability of systemic ethanol to increase dopamine release in the nucleus accumbens when the antagonists are infused into the VTA. PUBLIC HEALTH RELEVANCE The results of these studies will clarify a novel mechanism that is a significant component of the action of ethanol on the brain`s reward pathways. A better understanding of cellular mechanisms of alcohol addiction will improve the treatment and prevention of alcoholism.