Synaptic Mechanisms of General Anesthetic Action

描述(申请人提供)：我们的长期目标是了解全身麻醉药对突触传递的作用机制。了解现有全身麻醉药的治疗和不良反应的机制将有助于安全和适当的临床使用，同时使更多特定药物的合理开发和副作用减少。我们的假设是，全麻药通过药物特异性和递质特异性突触前机制影响神经递质的释放。主要目标将通过结合神经化学和新的神经生理学方法来实现，具体目标如下：1)通过表征突触前全身麻醉效应的膜分隔机制(如离子通道或受体介导)和细胞内机制(如融合/胞吐机制)，确定挥发性麻醉剂抑制递质释放的机制。本课程将评估突触前电压门控离子通道、配基门控离子通道和囊泡融合蛋白作为麻醉药靶点的作用。2)采用大鼠神经垂体神经末梢全终末膜片钳记录技术，观察全身麻醉药对突触前离子通道的电生理作用。3)阐明麻醉药对神经递质释放的特异性和脑区特异性的影响。神经化学技术将被用来确定全麻药对大鼠皮质神经末梢谷氨酸释放的抑制是否可以推广到其他中枢神经系统区域和其他递质类别。拟议的实验使用从大鼠中枢神经系统不同区域分离的神经末梢来研究亚细胞部分的突触前麻醉效应，该部分不存在细胞间相互作用，并适用于药理学和电生理分析。使用的方法包括对具有代表性的静脉麻醉药和挥发性麻醉药对内源性和放射性标记递质自发和诱发释放的影响的神经化学分析，以及对分离的神经末梢突触前离子通道的电生理记录。阐明全麻药的突触前效应及其机制对于了解这类临床上重要的药物对神经功能的分子和细胞作用是至关重要的。

DESCRIPTION (provided by applicant): Our long-term goals are to understand the mechanisms of action of general anesthetics on synaptic transmission. Understanding the mechanisms of both the therapeutic and undesired effects of existing general anesthetics will facilitate safe and appropriate clinical use while enabling rational development of more specific agents with reduced side-effects. Our hypothesis is that general anesthetics affect neurotransmitter release by agent-specific and transmitter-specific presynaptic mechanisms. The major goals will be accomplished by combining neurochemical and novel neurophysiological approaches outlined in the following proposed Specific Aims: 1) Determine the mechanisms by which volatile anesthetics inhibit transmitter release by characterizing both membrane delimited (e.g. ion channel or receptor mediated) and intracellular (e.g. involving fusion/exocytosis machinery) mechanisms of presynaptic general anesthetic effects. The involvement of presynaptic voltage-gated ion channels, ligand-gated ion channels, and vesicle fusion proteins as targets for anesthetics will be assessed. 2) Determine the electrophysiological effects of general anesthetics on presynaptic ion channels using whole-terminal patch clamp recording techniques of isolated rat neurohypophysial nerve terminals. 3) Elucidate transmitter-specific and brain region-specific effects of anesthetics on neurotransmitter release. Neurochemical techniques will be used to determine whether inhibition of glutamate release by general anesthetics in rat cortical nerve terminals can be generalized to other CNS regions and to other transmitter classes. The proposed experiments employ nerve terminals isolated form various regions of the rat CNS to study presynaptic anesthetic effects in a subcellular fraction that is free of intercellular interactions and amenable to pharmacological and electrophysiological analysis. Methods to be used include neurochemical analysis of the effects of representative intravenous and volatile anesthetics on spontaneous and evoked release of endogenous and radiolabeled transmitters and electrophysiological recordings of presynaptic ion channels in isolated nerve terminals. Elucidation of the presynaptic effects of general anesthetics and their mechanisms is essential to understanding the molecular and cellular actions of this clinically important class of drugs on neuronal function.