Volatile Anesthetic Actions on Synaptic GABAA Receptors

描述（由申请人提供）：全身麻醉剂通过未知的机制改变大脑功能。尽管许多证据表明GABAA受体是一个关键靶点，但受体功能变化与行为终点之间的因果关系尚未很好地建立，麻醉剂改变通道功能的分子机制尚未确定。本研究的目的是将麻醉药对GABAA受体的分子作用与特定的行为效应联系起来。该策略将重点放在抑制海马体上，海马体是一种在记忆中起重要作用的大脑结构，特别容易引起癫痫发作。为了实现这一目标，确定了三个具体目标：1)验证挥发性麻醉剂和相关药物的健忘症和惊厥特性是由它们对体外观察到的不同类型的GABAA反应的作用引起的；2)确定麻醉剂改变了哪些GABAA受体通道动力学参数，以及这些变化如何导致抑制性突触电流延长；3)确定挥发剂阻断GABAA受体的结构和动力学基础。实验将使用电生理技术来记录海马神经元对麻醉剂、非固定剂和促惊厥剂的反应。将比较不同受体群体的反应，以测试与特定行为的关联。麻醉作用的动力学机制将通过快速溶液交换技术、单通道记录和重组受体进行研究。结果将用标准的和新开发的变构动力学模型来解释。与通道阻滞相关的结构特征将使用由α和γ亚基产生的嵌合受体来确定，这两个亚基对阻滞的易感性有很大的不同。这些结果将为麻醉作用的细胞和分子基础提供新的信息。这些药物被广泛使用，了解它们产生有益效果和有害副作用的机制将有助于更安全地使用现有药物和开发更安全的新化合物。

DESCRIPTION (provided by applicant): General anesthetics alter brain function via mechanisms that remain unknown. Although much evidence points to the GABAA receptor as a key target, causal relationships between changes in receptor function and behavioral end points have not yet been well established, and molecular mechanisms by which anesthetics alter channel function have not been determined. The goal of the proposed research is to relate molecular actions of anesthetics on GABAA receptors to specific behavioral effects. The strategy is to focus on inhibition in the hippocampus, a brain structure that plays an important role in memory and is particularly susceptible to development of seizure activity. To accomplish this goal, three specific aims are identified: 1) Test the hypothesis that the amnestic and convulsant properties of volatile anesthetics and related agents in vivo result from their actions on separate types of GABAA responses that are observed in vitro; 2) Determine which GABAA receptor channel kinetic parameters are altered by anesthetics, and how these changes cause inhibitory synaptic currents to be prolonged; 3) Determine the structural and kinetic basis of GABAA receptor block by volatile agents. Experiments will be conducted using electrophysiological techniques to record the responses of hippocampal neurons to anesthetics, non-immobilizers, and pro-convulsant agents. Responses of different receptor populations will be compared to test for associations with behaviorally specific actions. Kinetic mechanisms of anesthetic action will be investigated using rapid solution exchange techniques, single channel recordings, and recombinant receptors. Results will be interpreted in terms of standard and newly developed allosteric kinetic models. Structural features associated with channel block will be determined using chimeric receptors created from alpha and gamma subunits, which differ substantially in susceptibility to block. These results will provide new information regarding the cellular and molecular bases of anesthetic action. These drugs are widely used, and understanding the mechanisms by which they produce their beneficial effects and detrimental side-effects will enable the safer use of existing agents and the development of safer new compounds.