Synaptic Mechanisms of General Anesthetic Action

摘要 尽管临床应用广泛，但对全身麻醉药的作用机制的了解还不足以解释。 它们如何导致健忘症、意识丧失或静止(随着剂量的增加)，主要特征 全身麻醉。这个项目的长期目标是定义构成其基础的突触机制 全麻药对中枢神经系统的作用。麻醉药对突触具有强大而特异的作用 传递，包括突触前对神经递质释放的作用和突触后作用 在受体和树突棘上。这项研究计划的主要目标是了解突触- 挥发性麻醉剂的特定突触前效应还知之甚少。我们的中心假设是 全麻药具有突触特异性机制，导致对突触前离子的选择性作用 通道和胞吐作用。这一建议的基本原理是理解突触前麻醉剂 与治疗性(昏迷、健忘、静止)和毒性(神经毒性、认知功能障碍)相关的行动 麻醉药的功能障碍、呼吸和心血管抑制)对开发新的 副作用改善的麻醉药和用于优化当前麻醉技术的越来越多 高危患者。我们的建议是，挥发性麻醉剂对多种药物的释放有明显的影响 麻醉敏感离子通道在突触前的不同表达所致的神经递质 递质释放，特别是电压门控的钠和钙通道，在方法和 在神经科学和结构生物学方面采用了最近发展起来的技术。中心假设将是 通过以下三个具体目标使用综合和协作的多学科方法进行测试 采用活体、细胞和分子方法：1)识别神经末梢特定的突触前机制 影响突触小泡胞吐对挥发性麻醉药的敏感性来检验这一假设 挥发性麻醉药通过神经末梢特异性机制不同地抑制突触囊泡的胞吐 由突触前离子通道的异质性表达引起；2)确定挥发油的作用 麻醉药对神经细胞内钙离子的调节及其对突触囊泡胞吐的影响 挥发性麻醉剂对细胞内钙动力学的影响影响突触囊泡胞吐作用的假说； 3)利用细菌识别电压门控钠通道上的挥发性麻醉剂结合部位 使用同源Navms来验证挥发性麻醉剂抑制涉及直接相互作用的假设。这个 研究在应用多学科和互补的电生理学、生物物理学和 涉及专家合作者团队的成像方法。预期的结果是一种分子 对理想和潜在毒性麻醉效果背后的突触麻醉机制的理解 关于兴奋性和抑制性突触传递。我们的研究结果将对合理使用产生积极的影响 全麻药作为一类日益重要的基本药物，对其未来的发展具有重要的意义。

Abstract Despite widespread clinical use, knowledge of the mechanisms of general anesthetics is insufficient to explain how they produce amnesia, unconsciousness or immobilization (with increasing doses), the cardinal features of general anesthesia. The long-term goal of this project is to define the synaptic mechanisms that underlie the actions of general anesthetics on the CNS. Anesthetics have potent and specific effects on synaptic transmission, including both presynaptic actions on the release of neurotransmitters and postsynaptic actions on receptors and dendritic spines. The principal objective of this research proposal is to understand synapse- specific presynaptic effects of volatile anesthetics which are poorly understood. Our central hypothesis is that general anesthetics have synapse-specific mechanisms resulting in selective effects on presynaptic ion channels and exocytosis. The rationale underlying this proposal is that understanding presynaptic anesthetic actions relevant to their therapeutic (unconsciousness, amnesia, immobility) and toxic (neurotoxicity, cognitive dysfunction, respiratory and cardiovascular depression) effects of anesthetics is essential for developing new anesthetics with improved side-effect profiles and for optimizing current anesthetic techniques in increasingly high-risk patients. Our proposal that volatile anesthetics have distinct effects on the release of various neurotransmitters due to differential presynaptic expression of anesthetic-sensitive ion channels coupled to transmitter release, in particular voltage-gated sodium and calcium channels, is innovative in approach and employs recently developed techniques in neuroscience and structural biology. The central hypothesis will be tested using an integrative and collaborative multidisciplinary approach by the following three specific aims employing in vivo, cellular and molecular methods: 1) Identify nerve terminal-specific presynaptic mechanisms that influence the sensitivity of synaptic vesicle exocytosis to volatile anesthetics to test the hypothesis that volatile anesthetics differentially inhibit synaptic vesicle exocytosis by nerve terminal-specific mechanisms resulting from heterogeneous presynaptic ion channel expression; 2) Determine the effects of volatile anesthetics on neuronal intracellular Ca2+ regulation and its impact on synaptic vesicle exocytosis to test the hypothesis that volatile anesthetic effects on intracellular Ca2+ dynamics influence synaptic vesicle exocytosis; and 3) Identify volatile anesthetic binding sites on voltage-gated sodium channels using the bacterial homologue NavMs to test the hypothesis that volatile anesthetic inhibition involves direct interactions. The research is significant in applying multidisciplinary and complementary electrophysiological, biophysical, and imaging approaches involving a team of expert collaborators. The expected outcome is a molecular understanding of synaptic anesthetic mechanisms underlying desirable and potentially toxic anesthetic effects on excitatory and inhibitory synaptic transmission. Our results will have positive impact on the rational use and future development of general anesthetics, an increasingly important class of essential medicines.