Schwarz J R
Physiologisches Institut, Universität Hamburg.
EEG EMG Z Elektroenzephalogr Elektromyogr Verwandte Geb. 1988 Sep;19(3):115-22.
A comparison of the ionic currents in single myelinated nerve fibres isolated from the sciatic nerve of the rat and the frog was performed. The nodal membrane of rats lacked almost totally potential dependent potassium channels, whereas in the frog large potassium currents were recorded. Therefore, it was concluded that in mammalian nerve fibres repolarization of the action potential is brought about by the unspecific leakage current and the inactivation of the sodium channels. Phenytoin and tocainide reduced the Na current in nerve fibres of both species. This reduction was due to a potential and frequency dependent block of sodium channels. 50 microM phenytoin and 200 microM tocainide shifted the inactivation curve of the sodium system by 25 mV to more hyperpolarizing membrane potentials. In addition, a decrease in the time interval between repetitive depolarizations increased the amount of Na current reduction. This suggested that in the presence of the drugs the equilibrium between resting and inactive sodium channel states was shifted to more inactivation. The results were successfully interpreted in terms of the "modulated receptor hypothesis".
对从大鼠和青蛙坐骨神经分离出的单根有髓神经纤维中的离子电流进行了比较。大鼠的结区膜几乎完全缺乏电压依赖性钾通道，而在青蛙中则记录到较大的钾电流。因此，得出结论：在哺乳动物神经纤维中，动作电位的复极化是由非特异性漏电流和钠通道失活引起的。苯妥英和妥卡尼降低了两种动物神经纤维中的钠电流。这种降低是由于钠通道的电压和频率依赖性阻滞。50微摩尔苯妥英和200微摩尔妥卡尼使钠系统的失活曲线向更超极化的膜电位方向移动了25毫伏。此外，重复去极化之间的时间间隔缩短会增加钠电流降低的幅度。这表明在药物存在的情况下，静息和失活钠通道状态之间的平衡向更多失活方向移动。根据“调制受体假说”成功地解释了这些结果。
