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

描述(申请人提供)：在美国，酗酒每年导致100,000多人死亡，经济损失超过1800亿美元；据进一步估计，医院里几乎一半的患者都有因饮酒而加剧的健康问题。如此巨大的成本促使人们进行密集的研究，以了解这种药物是如何影响大脑功能的。然而，尽管有这些努力，关于乙醇在神经元水平上是如何起作用的，还没有达成共识。一种流行的假说是，乙醇增强了大脑中GABAA受体介导的信号传递功能，但是否涉及特定的GABAA受体亚型，如果是的话，乙醇如何增强其功能仍是悬而未决的问题。我们先前的工作表明，含有d亚单位的突触外GABAA受体亚型是在适度社交消费期间实现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突触外GABAA受体重组和天然版本敏感性的关键因素。这笔赠款分为三个目标。目的1建议利用一种新的“功能标签”，即d亚基上的单一氨基酸取代，使其对苯二氮类药物敏感。该标签将允许我们仔细地将该亚基的存在或不存在与乙醇敏感性相关联。目的2利用化学笼子中的GABA的激光光解，将乙醇和其他GABAA受体调节剂的敏感性映射到小脑神经元上。目的3验证d亚基掺入使重组和天然GABAA受体对镇静催眠药Gaboxadol/THIP具有纳摩尔敏感性的假设。这种区别药理学将解释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包含GABAA受体的d亚基的工具。从这些实验中获得的知识将让我们更彻底地了解酒精和镇静催眠药物是如何影响大脑功能的。特别是，这些结果应该确定一个关键的乙醇靶标对急性酒精中毒的贡献。在分子水平上识别酒精靶点是开发治疗酒精相关性认知障碍和酒精成瘾的合理疗法的先决条件。公共卫生相关性：我们建议研究酒精在突触外GABAA受体上作用的分子细节，GABAA受体是抑制性神经递质受体的一个子集，被认为是急性酒精作用和适应长期酒精暴露的关键靶标。验证这类令人兴奋的新的酒精靶点并确定酒精作用的决定因素将使开发新的疗法来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.