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

描述（由申请人提供）：在美国，每年酒精滥用导致超过100，000人死亡，并导致超过1800亿美元的经济成本;据进一步估计，医院中几乎一半的患者因酒精使用而加剧健康问题。如此巨大的成本促使人们进行深入的研究，以了解这种药物如何影响大脑功能。然而，尽管有这些努力，乙醇如何在神经元水平上发挥作用还没有达成共识。一个流行的假设是，乙醇增强了大脑中GABAA受体介导的信号传导的功能，但是否涉及特定的GABAA受体亚型，如果是这样，乙醇如何增强其功能是未回答的问题。我们先前的工作表明，含有d亚基的突触外GABAA受体亚型是在适度的社会消费过程中实现低浓度乙醇的重要目标。在一个合作的努力，我们建议系统地研究影响重组和天然版本的突触外GABAA受体的敏感性的关键因素。这笔赠款分为三个目标。目的1提出利用一种新的“功能标签”，在d亚基中的一个单一的氨基酸取代，这使得它对苯二氮卓类药物敏感。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GABA激光光解映射敏感性乙醇和其他GABAA受体调节剂小脑神经元。目的3测试的假设，d亚基掺入赋予重组和天然GABAA受体与纳摩尔敏感性的镇静催眠药物加波沙朵/THIP。这种区别性药理学将解释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透彻地了解酒精和镇静催眠药物如何影响大脑功能。特别是，研究结果应确定一个关键的乙醇目标急性酒精中毒的贡献。酒精靶点的分子水平鉴定是开发治疗酒精相关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：我们建议研究乙醇作用于突触外GABAA受体的分子细节，该受体是抑制性神经递质受体的一个子集，在急性酒精作用和适应慢性酒精暴露中都是关键靶点。验证这种令人兴奋的新类别的乙醇目标和确定乙醇作用的决定因素将使新的治疗方法能够解决酒精成瘾和酒精中毒期间发生的脑功能的慢性变化。

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.