Frankenhaeuser B, Arhem P
Philos Trans R Soc Lond B Biol Sci. 1975 Jun 10;270(908):515-25. doi: 10.1098/rstb.1975.0028.
The membrane potential in single nodes of Ranvier was changed in rectangular pulse steps while the membrane currents, associated with the potential steps, were measured. Changes were made in the ionic composition of the external and the internal medium. The latter changes were obtained by free diffusion through a cut internode. The steady state currents, described on the basis of potassium and leak permeability, were affected by the solution composition in a characteristic way. Increased inside concentration of sodium and lithium caused a striking rectification of the outward steady state currents at large potential steps. Instantaneous potassium currents in high [K+]o at a second potential step to E approximately equal to minus 80 mV were not affected by [Na+]1. Neither [Na+]o nor [K+]i affected the potential at which this rectification appeared. Increased [K+]o shifted the region for rectification along the potential axis in positive direction. These findings form strict limitations for satisfactory models describing the mechanism for the steady state current in myelinated nerve.
在对单个郎飞结的膜电位施加矩形脉冲阶跃变化的同时，测量与这些电位阶跃相关的膜电流。对细胞外和细胞内介质的离子组成进行了改变。后者的改变是通过切开的节间段自由扩散实现的。基于钾离子和漏电导率描述的稳态电流，受到溶液组成的特征性影响。细胞内钠离子和锂离子浓度的增加，在较大电位阶跃时导致外向稳态电流出现显著的整流现象。在第二个电位阶跃至约-80 mV的高细胞外钾离子浓度下，瞬时钾电流不受细胞内钠离子浓度的影响。细胞外钠离子浓度和细胞内钾离子浓度均不影响这种整流现象出现时的电位。细胞外钾离子浓度的增加使整流区域沿电位轴正向移动。这些发现对描述有髓神经稳态电流机制的理想模型构成了严格限制。
