Schwarz J R, Reid G, Bostock H
Physiologisches Institut, Universitätskrankenhaus Eppendorf, Hamburg, Germany.
Pflugers Arch. 1995 Jun;430(2):283-92. doi: 10.1007/BF00374660.
Action potentials and membrane currents were recorded in single human myelinated nerve fibres under current- and voltage-clamp conditions at room temperature. Nerve material was obtained from patients undergoing nerve graft operations. Successful recordings were made in 11 nerve fibres. In Ringer's solution, large transient Na currents were recorded, which could be blocked completely with tetrodotoxin. Partial block of these currents with 3 nM tetrodotoxin was used to reduce the voltage-clamp error due to series resistance. Outward K currents were very small in intact nerve fibres, but had a large amplitude in fibres showing signs of paranodal demyelination. In isotonic KCl, the K current could be separated into three components: two fast components (Kf1 and Kf2) and one slow component (Ks). Time constants and steady-state activation and inactivation of Na permeability and of fast and slow K conductance were measured within the potential range of -145 mV to +115 mV. From these parameters, the corresponding rate constants were calculated and a mathematical model based on the Frankenhaeuser-Huxley equations was derived. Calculated action potentials closely matched those recorded. Single calculated action potentials were little affected by removing the fast or slow K conductance, but the slow K conductance was required to limit the repetitive response of the model to prolonged stimulating currents.
在室温下，于电流钳和电压钳条件下，在单根人有髓神经纤维中记录动作电位和膜电流。神经材料取自接受神经移植手术的患者。在11根神经纤维中成功进行了记录。在林格氏液中，记录到了大的瞬时钠电流，该电流可被河豚毒素完全阻断。用3 nM河豚毒素部分阻断这些电流，以减少由于串联电阻引起的电压钳误差。完整神经纤维中的外向钾电流非常小，但在显示结旁脱髓鞘迹象的纤维中具有很大的幅度。在等渗氯化钾中，钾电流可分为三个成分：两个快速成分（Kf1和Kf2）和一个慢速成分（Ks）。在-145 mV至+115 mV的电位范围内，测量了钠通透性以及快速和慢速钾电导的时间常数、稳态激活和失活。根据这些参数计算出相应的速率常数，并推导了基于弗兰肯豪泽-赫胥黎方程的数学模型。计算得到的动作电位与记录到的动作电位紧密匹配。去除快速或慢速钾电导对单个计算得到的动作电位影响很小，但需要慢速钾电导来限制模型对延长刺激电流的重复反应。
