Ethanol sensitivity in delta subunit-containing GABA(A) receptors

描述（由申请人提供）：在美国，酗酒每年导致10万多人死亡，造成的经济损失超过1800亿美元；据进一步估计，几乎一半住院病人的健康问题因饮酒而加剧。如此巨大的成本促使人们深入研究这种药物是如何影响大脑功能的。然而，尽管做出了这些努力，对于乙醇在神经元水平上的作用仍没有达成共识。一个普遍的假设是，乙醇增强了GABAA受体介导的脑信号功能，但是否涉及特定的GABAA受体亚型，如果有的话，乙醇如何增强其功能是没有答案的问题。我们之前的研究表明，含有d亚基的GABAA受体的胞外异构体是在适度社会消费过程中获得低浓度乙醇的重要靶点。在一项合作努力中，我们建议系统地检查影响重组和天然版本的突触外GABAA受体敏感性的关键因素。这项资助分为三个目的。目的1提出利用一种新的“功能标签”，即d亚基中的单氨基酸取代，使其对苯二氮卓类药物敏感。该标签将使我们能够仔细地将该亚基的存在或缺失与乙醇敏感性联系起来。目的2利用激光光解化学笼的GABA来绘制对乙醇和其他GABAA受体调节剂在小脑神经元上的敏感性。目的3验证了d亚基掺入使重组和天然GABAA受体对镇静催眠药物加博沙多/THIP具有纳摩尔敏感性的假设。这种区别性药理学可以解释THIP作为镇静剂的强大行为作用，并将验证该化合物作为选择性激活含有GABAA受体的d亚基的工具。从这些实验中获得的知识将使我们更彻底地了解酒精和镇静催眠药物如何影响大脑功能。特别是，结果应该确定一个关键的乙醇目标对急性酒精中毒的贡献。乙醇靶点的分子水平鉴定是开发合理治疗酒精相关认知障碍和酒精成瘾的先决条件。公共卫生相关性：我们建议研究乙醇作用于突触外GABAA受体的分子细节，GABAA受体是抑制性神经递质受体的一个子集，是急性酒精作用和慢性酒精暴露适应的关键靶点。验证这一令人兴奋的新型乙醇靶点和确定乙醇作用的决定因素将有助于开发新的治疗方法，以解决酒精成瘾和酒精中毒期间发生的大脑功能的慢性变化。

DESCRIPTION (provided by applicant): Each year in the United States alcohol abuse leads to more than 100,000 deaths and results in economic costs of more than 180 billion dollars; it is further estimated that almost half of all patients in hospitals have health problems exacerbated by alcohol use. Such tremendous costs have motivated intensive research efforts to understand how this drug affects brain function. Yet despite these efforts, there is no consensus as to how ethanol acts at a neuronal level. A prevailing hypothesis has been that ethanol enhances the function of GABAA receptor-mediated signaling in brain but whether specific GABAA receptor subtypes are involved, and if so how ethanol enhances their function are unanswered questions. Our prior work has suggested that d subunit-containing, extrasynaptic isoforms of GABAA receptors are important targets for the low concentrations of ethanol achieved during moderate social consumption. In a collaborative effort, we propose to systematically examine key factors that influence the sensitivity of recombinant and native versions of extrasynaptic GABAA receptors. The grant is organized into three aims. Aim 1 proposes to make use of a novel "functional tag", a single amino acid substitution in the d subunit, which renders it sensitive to benzodiazepines. The tag will allow us to carefully correlate the presence or absence of this subunit with ethanol sensitivity. Aim 2 utilizes laser photolysis of chemically caged GABA to map sensitivity to ethanol and to other GABAA receptor modulators on cerebellar neurons. Aim 3 tests the hypothesis that d subunit incorporation endows both recombinant and native GABAA receptors with nanomolar sensitivity to the sedative hypnotic drug Gaboxadol/THIP. Such discriminative pharmacology would explain the powerful behavioral actions of THIP as a sedative and would validate the compound as a tool for selectively activating d subunit containing GABAA receptors. The knowledge obtained from these experiments will give us a more thorough understanding of how alcohol and sedative hypnotic drugs affects brain function. In particular, the results should define the contributions of a key ethanol target to acute alcohol intoxication. Molecular level identification of ethanol targets is a prerequisite for the development of rational therapies to treat alcohol-related cognitive impairment and alcohol addiction. PUBLIC HEALTH RELEVANCE: We propose to study the molecular details of ethanol action at extrasynaptic GABAA receptors, a subset of inhibitory neurotransmitter receptors implicated as key targets in both acute alcohol action and in adaptation to chronic alcohol exposure. Validation of this exciting new class of ethanol targets and identification of the determinants of ethanol action will enable the development of new therapies to address alcohol addiction and the chronic changes in brain function that occur during alcoholism.