Ion channels and their functions at the node of Ranvier of mammalian somatosensory afferent fibers

郎维氏结是感觉、运动和神经元的有髓神经纤维上高度特化的轴突区域。 动作电位通过跳跃式传导传播的中枢神经系统。 通过郎维氏结的跳跃传导确保及时的感觉和运动反应以及精确的信号 在CNS中处理。许多神经系统疾病影响朗维尔结， 传导导致运动障碍，例如麻痹和感觉功能障碍，例如疼痛，麻木， 和其他异常感觉。对哺乳动物朗氏结离子通道及其功能的认识 是充分理解生理和病理条件下跳跃传导的关键， 这些感觉和运动障碍的潜在治疗。本项目的总体目标是研究离子 通道机制，以确保跳跃传导的动作电位在哺乳动物节点的兰维尔。 我们最近发展了原位膜片钳记录技术的郎维尔节点， 大鼠的躯体感觉传入纤维。在初步的研究中，我们发现，节点的兰维尔表达， 令人惊讶的高水平的双孔结构域钾通道（K2P通道），一个独特的离子通道家族， 组成性开放的通道，以及其在动作电位和神经传导中的功能 是以前未知的。在功能上，我们的初步研究强烈表明，K2P通道是关键， 在哺乳动物的有髓躯体感觉传入纤维中用于确保跳跃传导的分子。在这 应用方面，我们将结合药理学、基因组学、细胞生物学和细胞生物学等技术， 敲除和免疫化学方法来实现以下特定目的。目标1.表征 K2P通道及其分子特性的研究 传入纤维在这个目标中，我们将在Ranvier结处确定K2P通道亚型，并对其进行分析。 药理学和单通道特性。目标2.研究K2P通道在保护 大鼠躯体感觉传入纤维Ranvier结的跳跃性传导。这一目标将阐明 郎维叶结的K2P通道在快速动作电位复极化和 确保高速和高频跳跃传导。目标3：说明K2P通道在 Ranvier结在大鼠体感温度依赖性跳跃传导中起关键作用 传入纤维这一目标将测试在Ranvier节点处的K2P通道是高度热的想法 敏感，这是控制跳跃传导的速度和保真度的决定性因素， 温度这一目的证实了影响K2P通道活性的生物学因素将高度影响K2P通道的活性。 有髓神经纤维的跳跃传导。这3个目标的完成将阐明一种新的离子通道 一种确保跳跃传导的机制，可能与感觉和运动障碍有关 兰维尔结跳跃性传导受损

Nodes of Ranvier are highly specialized axonal regions on myelinated nerve fibers of sensory, motor and central nervous systems where action potentials are propagated by saltatory (leap in Latin word) conduction. Saltatory conduction through nodes of Ranvier ensures timely sensory and motor responses and precise signal processing in the CNS. A number of neurological diseases affect nodes of Ranvier to impair saltatory conduction leading to motor disorders, such as paralysis and sensory dysfunctions, such as pain, numbness, and other abnormal sensations. Knowledge of ion channels and their functions at mammalian nodes of Ranvier is a key to fully understanding saltatory conduction under both physiological and pathological conditions, and for potential treatments of those sensory and motor disorders. The overall goal of this project is to study ion channel mechanisms for securing saltatory conduction of action potentials at mammalian nodes of Ranvier. We have recently developed the in situ patch-clamp recording technique for nodes of Ranvier in somatosensory afferent fibers of rats. In the preliminary studies we have found that nodes of Ranvier express surprisingly high levels of the two-pore domain potassium channels (K2P channels), a unique family of ion channels that constitutively open, and the function of which, in action potentials, as well as in nerve conduction was previously unknown. Functionally, our preliminary studies strongly suggest that K2P channels are key molecules for securing saltatory conduction in myelinated somatosensory afferent fibers of mammals. In this application, we will use the in situ patch-clamp recording technique in conjunction with pharmacology, gene knockdown, and immunochemistry approaches to achieve the following specific aims. Aim 1. Characterize K2P channels and elucidate their molecular identities at the node of Ranvier of rat somatosensory afferent fibers. In this aim we will pin down K2P channel subtypes at the node of Ranvier and profile their pharmacological and single channel properties. Aim 2. Study specific roles of K2P channels in securing saltatory conduction at the node of Ranvier of rat somatosensory afferent fibers. This aim will elucidate that the K2P channels at the node of Ranvier play a key role in rapid action potential repolarization and in securing high speed and high frequency saltatory conduction. Aim 3. Elucidate that K2P channels at the node of Ranvier play a key role in temperature-dependent saltatory conduction on rat somatosensory afferent fibers. This aim will test the idea that K2P channels at the node of Ranvier are highly thermal sensitive, which is a determinant factor controlling the velocity and fidelity of saltatory conduction at different temperatures. This aim exemplifies that biological factors affecting K2P channel activity will highly impact saltatory conductions in myelinated nerve fibers. Completion of the 3 Aims will elucidate a novel ion channel mechanism that secures saltatory conduction, which may have implications in sensory and motor disorders with impaired saltatory conduction at the node of Ranvier.