无髓鞘神经纤维兴奋后传导速度的变化

Variability of conduction velocity in unmyelinated nerve fibers after excitation

目的：观察Ｃ纤维兴奋后传导速度是否变化及其变化规律．方法：在麻醉大鼠的尾神经上剥制细束，引导单根Ｃ纤维的传入放电，以单次或不同频率的方形脉冲刺激皮肤感受野或尾神经外周端，测定Ｃ纤维在不同条件刺激兴奋后动作电位传导速度的变化．结果：Ｃ纤维兴奋后的一定时间内传导速度发生变化，大部分平均减慢（７．２６±２．９９）％，小部分平均增快（１．６９±１．２０）％，并且可经一定静息的时间恢复至初始传导速度．随着刺激频率的增加或刺激时间的延长，变速期逐渐延长．结论：Ｃ纤维兴奋后传导速度经历一个变速期。

Objective: To observe the variability of conduction velocity of C fibers after excitation and its regulations. Methods: Afferent discharges of single unit C fibers were recorded after exposure of the caudal nerve fibers in an anesthetized SD rat. The square waves of a single pulse or different frequencies were employed to stimulate the cutaneous receptive fields and peripheral parts of the candal nerve in order to determine the variations of conduction velocity (CV) of action potential subjected to different conditional stimulation. Results: After excitation, CV of C fibers varied in some time, majority of that slowed (7.26±2.99)% and minority of that fastened (1.69±1.20)% on the average, and the variable CV could recover to the original conduction velocity (CV 0) in some resting time. With increasing the stimulating frequency or time, the alterable period showed increasing gradually. Conclusion: There is an alterable period of CV in C fibers after excitation. The variable ranges and the recovering time are related to the frequency and course of conditional stimulation.