以外周神经C-F传导丢锋为靶点的镇痛作用及机制研究

Previously, we found, from the investigation of sensory neuronal activity, that the peripheral nonmyelinated fiber (C-F) had integrating and processing effect on the pain signal transmitting on it. The main manifestation is through conduction velocity slowing and conduction failure. Among which, the reduction of the degree of the conduction failure results in the increase of the pain signal, then evokes hyperalgesia. Accordingly, we propose that during the process of transmitting peripheral pain signal, conduction failure is used by C-F to modulate the propagating frequency and transmitting pattern in a self negative feedback manner. Under the help of combination of various biological techniques as well as the mathematical operation, the present project aim to explore the basic rule of conduction failure. And then how the interaction among Ih current and calcium-dependent potassium current contributes to conduction failure, as well as the certain subtypes underlying the conduction failure will be illuminated. Finally, the novel analgesic methods targeting at modulating conduction failure will be established. This investigation will amend the traditional concept about the faithful propagation of C-F, contribute to the exploration of the basic rule for conduction failure of C-F, and also provide the experimental and theoretical evidence for creating peripheral analgesic strategy with little side effect.

我室既往研究发现外周无髓鞘神经纤维（C-F）通过传导速度减慢和传导丢峰程度的变化等方式对痛信号的传导有整合加工作用。其中, C-F传导丢峰程度的降低是导致痛信号传入增多，进而诱发痛觉过敏的重要环节。据此，我们设想外周C-F在传导痛信号过程中，可能通过传导丟峰等方式对痛信号的传导频率和模式进行自我负反馈调制。本项目将通过电生理与形态及分子生物学技术的结合，联系理论模型的运算与验证，揭示C-F传导丢锋的基本规律，阐明超极化激活阳离子（HCN）通道与钙激活钾（K(Ca)）通道中各特定亚型介导的通道电流在传导丢锋发生过程中的相互作用。并以此为基础，建立并验证以调控传导丢锋为靶位的外周镇痛新疗法。研究结果将修正C-F单纯传导动作电位的传统概念，发现C-F传导丢锋基本活动规律，阐明C-F调变痛信号的传导丢锋机制，为创建副作用小的选择性外周镇痛新疗法提供实验和理论依据。

我室既往研究发现外周无髓鞘神经纤维（C-F）通过传导速度减慢和传导丢峰程度的变化等方式对痛信号的传导有整合加工作用。其中, C-F传导丢峰程度的降低是导致痛信号传入增多，进而诱发痛觉过敏的重要环节。本课题在癌痛模型上对此进行进一步验证，以期明确C-F传导丢峰程度的降低导致慢性痛痛觉过敏产生的普遍性规律。在成功创建跟骨癌痛模型的基础上，与正常动物相比，外周C纤维的传导丢峰程度明显减弱。在离体背根神经节带外周神经标本上进行记录，在神经干中部滴加ZD7288，可致放电节律改变，总体频率呈浓度依赖性降低，故推测ZD7288可以改变癌痛模型传导丢峰程度。对传导丢锋离子通道机制的探讨过程中，我们发现除了Ih电流的变化外，癌痛模型的DRG小神经元全细胞总K +电流持续下降，格列本脲(10μM)可翻转此作用。癌痛模型组减弱的传导丢峰在加入KATP通道的阻断剂格列本脲后，丢锋程度显著增强。行为学检测发现，在动物进行神经干周围注射格列本脲，发现动物痛过敏行为翻转，达到了明显的镇痛效果的同时没有运动功能障碍，而在神经干周围注射利多卡因（2％）在翻转痛敏的同时，也会影响动物的运动功能。相关结果在一定程度上论证了格列本脲基于传导丢峰的选择性外周镇痛效应。此外，我们对传导丢峰的调控机制进行了探讨，发现去甲肾上腺素（NE）会降低传导丢峰程度，且其作用下游离子通道也是KATP。在DRG小细胞H-H模型基础上，综合Ih及KATP通道电流的作用，初步模拟了传导丢锋的过程。课题研究发现了C-F传导丢锋基本活动规律，阐明C-F调变痛信号的传导丢锋机制，为创建副作用小的选择性外周镇痛新疗法提供了实验和理论依据