Zhu Zhi-Ru, Tang Xiao-Wei, Wang Wen-Ting, Ren Wei, Xing Jun-Ling, Zhang Jun-Ran, Duan Jian-Hong, Wang Yu-Ying, Jiao Xiying, Hu San-Jue
Department of Biomedical Engineeringe, Zhejiang University, Hangzhou, China.
Neurosignals. 2009;17(3):181-95. doi: 10.1159/000209279. Epub 2009 Mar 19.
Recent experimental and theoretical data indicate that the functional capabilities of axons with specialized structures are much more diverse than traditionally thought. However, few observations were concerned with the main axons without arborization. In the present study, electrical stimulation of the saphenous nerve at different frequencies (2, 5, 10, 20 Hz) was used to test the role of activity-dependent effects on the pattern of action potentials that propagate along individual unmyelinated fibers (C fibers) within the trunk of the saphenous nerve in rabbits. Three basic types of C fiber responses to repetitive stimulation were observed: type-1 fibers showed an entrained response without conduction failure; type-2 fibers discharged with intermittent conduction failures; while only sporadic conduction failures happened in type 3. The failure modality in type-2 and type-3 fibers is closely related to the conductive distance as well as the frequency and duration of stimuli which lead to a critical level of conduction velocity slowing. A novel fluctuation in interspike intervals was always observed immediately before the occurrence of the failures, implying that the fluctuation of conduction velocity is correlated with imminent failures. Both the 4-aminopyridine-sensitive potassium current and hyperpolarization-activated cation current were recognized to be involved in the regulation of conduction failure patterns. The results confirmed, at least in part, the existence of conduction failures in the main axon of C fibers, suggesting that axonal operations may also be determinants for adaptation phenomenon and information processing in peripheral nervous system.
最近的实验和理论数据表明，具有特殊结构的轴突的功能能力比传统认为的要多样化得多。然而，很少有观察涉及无分支的主要轴突。在本研究中，通过以不同频率（2、5、10、20赫兹）电刺激兔隐神经，来测试活动依赖性效应在沿隐神经干内单个无髓纤维（C纤维）传播的动作电位模式中的作用。观察到C纤维对重复刺激的三种基本反应类型：1型纤维表现为夹带反应且无传导失败；2型纤维放电时伴有间歇性传导失败；而3型纤维仅偶尔出现传导失败。2型和3型纤维的失败模式与传导距离以及导致传导速度减慢至临界水平的刺激频率和持续时间密切相关。在失败发生前总是能观察到峰间期的一种新的波动，这意味着传导速度的波动与即将发生的失败相关。4-氨基吡啶敏感钾电流和超极化激活阳离子电流都被认为参与了传导失败模式的调节。这些结果至少部分证实了C纤维主要轴突中存在传导失败，表明轴突活动也可能是外周神经系统适应现象和信息处理的决定因素。
