Synaptic Mechanisms of General Anesthetic Action

摘要 尽管广泛的临床使用，知识的机制，全身麻醉药是不够的，以解释 他们如何产生健忘症，无意识或固定（随着剂量的增加）， 全身麻醉这个项目的长期目标是确定突触机制， 全身麻醉药对中枢神经系统的作用。麻醉剂对突触有有效和特异性的作用， 传递，包括对神经递质释放的突触前作用和突触后作用 受体和树枝状棘上。这项研究的主要目的是了解突触- 挥发性麻醉剂的特定突触前效应，这是知之甚少。我们的核心假设是， 全身麻醉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。这一提议的基本原理是， 与其治疗（无意识、健忘、不动）和毒性（神经毒性、认知 功能障碍，呼吸和心血管抑制）的影响是必不可少的开发新的 具有改善的副作用特征的麻醉剂，以及用于优化当前麻醉技术， 高危患者。我们认为挥发性麻醉剂对各种药物的释放有不同的影响， 神经递质，由于麻醉敏感离子通道的突触前差异表达， 递质释放，特别是电压门控钠和钙通道，在方法上是创新的， 采用了神经科学和结构生物学的最新技术。核心假设是 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 采用体内、细胞和分子方法：1）识别神经末梢特异性突触前机制 影响突触囊泡胞吐作用对挥发性麻醉剂的敏感性，以检验以下假设： 挥发性麻醉药通过神经末梢特异性机制差异性地抑制突触囊泡胞吐作用 突触前离子通道表达的异质性; 2）确定挥发性 麻醉剂对神经元胞内Ca 2+调节及其对突触囊泡胞吐作用的影响，以测试 假设挥发性麻醉剂对细胞内Ca 2+动力学的影响影响突触囊泡胞吐作用; 和3）使用细菌鉴定挥发性麻醉剂在电压门控钠通道上的结合位点， 同源NavM来测试挥发性麻醉剂抑制涉及直接相互作用的假设。的 研究在应用多学科和互补的电生理学，生物物理学和 成像方法涉及一组专家合作者。预期的结果是一个分子 了解突触麻醉机制潜在的期望和潜在的毒性麻醉效果 兴奋性和抑制性突触传递。我们的研究结果将对合理使用 和未来发展的全身麻醉药，越来越重要的一类基本药物。

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.