Continuous conduction in demyelinated mammalian nerve fibres
Continuous conduction in demyelinated mammalian nerve fibres
复制标题
脱髓鞘哺乳动物神经纤维的连续传导
作者：
H. Bostock;T. Sears
有髓鞘的神经纤维以跳跃方式传导，内向膜电流的位点仅限于Ranvier结1。髓鞘的缺失导致结间传导时间长时间延迟、极端不应性和传导阻滞2。在研究的大老鼠腹根纤维的缓慢传导始终保持跳跃，与离散的网站内向电流，但有限的空间分辨率的方法使用阻止的结论是否有任何膜超出了原来的节点被激发。为了了解更多关于脱髓鞘暴露的结间轴突膜，我们使用了一种改进的外部纵向电流分析技术。更小的电极间距（120 µ m相对于400 - 600 µ m）提高了空间分辨率3，信号平均化使更小轴突的记录成为可能。我们已经发现，在这些纤维中，结间轴突膜不仅是电兴奋的，而且它可以支持跨脱髓鞘的结间的连续传导。这一结果为解释脱髓鞘疾病的影响提供了新的依据。
MYELINATED nerve fibres conduct in a saltatory fashion, with sites of inward membrane current restricted to the nodes of Ranvier1. Loss of myelin causes long delays in the inter nodal conduction time, extreme refractoriness and conduction block2. In the large rat ventral root fibres studied the slowed conduction always remained saltatory, with discrete sites of inward current, but the limited spatial resolution of the method used prevented conclusions about whether any membrane beyond that of the original nodes was excited. To find out more about the inter nodal axon membrane exposed by demyelination, we have used an improved technique of external longitudinal current analysis. A smaller electrode separation (120 µm as against 400–600 µm) has improved the spatial resolution3, and signal averaging has made possible recordings from smaller axons. We have found that in these fibres not only is internodal axon membrane electrically excitable, but that it can support continuous conduction across a demyelinated inter-node. This result provides a new basis for interpreting the effects of demyelinating disease.