Selective targeting of sodium channel blockers to pain-sensing neurons

项目总结/摘要 疼痛是通过在特定的初级感觉神经元群体中产生动作电位来发出信号的 被称为伤害感受器。最有效的止痛方法是 局部麻醉剂的施用，其通过抑制电压依赖性钠通道起作用， 从而抑制电兴奋性。临床使用的局部麻醉剂是至少存在于 部分以疏水、不带电的形式存在，可以通过细胞膜进入神经元。这些 麻醉剂进入并抑制所有神经元的兴奋性，而不仅仅是伤害感受器，因此可以有许多 除了阻断疼痛之外，还可以产生不期望的效果（包括麻痹和自主信号传导的阻断）。 这项拟议中的研究是基于最近的一项发现，即钠通道阻断药物可以被 选择性地靶向伤害感受器，通过共同应用利多卡因的永久带电衍生物（QX- 314)辣椒素是TRPV 1通道的激动剂支持这一假设的 该提案中的初步数据是，QX-314可以通过孔进入伤害感受器 由TRPV 1通道形成。拟议研究的总体目标是确定 TRPV 1激活剂和带电钠通道阻滞剂，可优化阻断神经元的兴奋性， 伤害感受神经元需要解决的具体问题包括： 有效进入带电钠通道阻滞剂？阻断剂进入的时间过程如何取决于 TRPV 1激动剂的性质和浓度阻滞剂进入和积累能否增强 通过激活蛋白激酶C是否有TRPV 1激动剂允许QX-314进入，而无需首先 刺激动作电位的放电细胞内QX-314阻断 不同类型的钠通道对伤害感受器的兴奋性很重要？ 这些问题将使用对天然TRPV 1通道的膜片钳实验来解决， 大鼠背根神经节神经元中的钠通道，以及使用异源 克隆的TRPV 1通道的表达。对这些机制的描述应有助于 开发基于带电钠靶向进入的疼痛缓解新临床治疗方法 传导阻滞剂进入痛觉神经元这样的治疗应该是非常有利的， 分娩、手术和牙科手术中的选择性疼痛缓解，以及可能用于某些形式的慢性疼痛， 神经性疼痛

Project Summary/ Abstract Pain is signaled by generation of action potentials in a specific population of primary sensory neurons known as nociceptors. The most effective form of pain relief without loss of consciousness is provided by administration of local anesthetics, which act by inhibiting voltage-dependent sodium channels and thereby depressing electrical excitability. Clinically-used local anesthetics are molecules that exist at least partially in a hydrophobic, uncharged form that can enter neurons through the cell membrane. These anesthetics enter and inhibit excitability in all neurons, not just nociceptors, and thus can have many undesirable effects (including paralysis and block of autonomic signaling) in addition to blocking pain. The proposed research is based on a recent finding that sodium channel blocking drugs can be targeted selectively to nociceptors by co-applying a permanently charged derivative of lidocaine (QX- 314) with capsaicin, an agonist for TRPV1 channels. The underlying hypothesis, supported by the preliminary data in the proposal, is that QX-314 can enter nociceptors by passing through the pore formed by TRPV1 channels. The overall goal of the proposed research is to identify combinations of TRPV1 activators and charged sodium channel blockers that optimize the block of excitability of nociceptive sensory neurons. Specific questions to be addressed include: What is the size limit for effective entry of charged sodium channel blockers? How does the time course of blocker entry depend on the nature and concentration of the TRPV1 agonist? Can blocker entry and accumulation be enhanced by activation of protein kinase C? Are there TRPV1 agonists that allow QX-314 entry without first stimulating firing of action potentials? What is the relative potency of intracellular QX-314 for blocking the different types of sodium channels known to be important for excitability of nociceptors? These questions will be addressed using patch clamp experiments on native TRPV1 channels and sodium channels in rat dorsal root ganglion neurons, with additional experiments using heterologous expression of cloned TRPV1 channels. Characterizing these mechanisms should facilitate the development of new clinical treatments for pain relief based on the targeted entry of charged sodium channel blockers into pain-sensing neurons. Such treatments should be highly advantageous for more selective pain relief in childbirth, surgery, and dental procedures and possibly for some forms of chronic neurogenic pain.