Szücs G, Kovács L, Cseri J, Gál J
Acta Physiol Hung. 1983;62(1):47-60.
The voltage dependent ionic conductances were studied by analysing the phase plane trajectories of action potentials evoked by electrical stimulation of the sartorius muscles of the frog (Rana esculenta). The delayed outward potassium current was measured also under voltage clamp conditions on muscle fibres of either the frog (Rana esculenta) or Xenopus laevis. On analysing the effect of physostigmine decreasing the peak amplitude, the rate of both the rising and falling phases of the action potentials, it was revealed that the alkaloid at a concentration of 1 mmol/l reduced significantly both the delayed potassium conductance and the outward ionic current values during the action potentials. The inhibition of sodium conductance and inward ionic current was less expressed. The maximum value of delayed potassium conductance measured under voltage clamp conditions was decreased by 1 mmol/l physostigmine. The time constant determined from the development of delayed potassium conductance was increased at a given membrane potential. The voltage vs. n relationship describing the membrane potential dependence of the delayed rectifier was not influenced by physostigmine. It has been concluded that physostigmine changes the time course of the action potentials by decreasing the value of both voltage dependent ionic conductances and by slowing down their kinetics. It is discussed that results obtained from the phase plane analysis of complex pharmacological effects can only be accepted with some restrictions.
通过分析电刺激食用蛙（Rana esculenta）缝匠肌诱发动作电位的相平面轨迹，研究了电压依赖性离子电导。还在电压钳制条件下，对食用蛙（Rana esculenta）或非洲爪蟾（Xenopus laevis）的肌纤维测量了延迟外向钾电流。在分析毒扁豆碱降低动作电位峰值幅度、上升相和下降相速率的作用时发现，浓度为1 mmol/l的生物碱显著降低了动作电位期间的延迟钾电导和外向离子电流值。对钠电导和内向离子电流的抑制作用较弱。在电压钳制条件下测得的延迟钾电导最大值，被1 mmol/l毒扁豆碱降低。在给定膜电位下，由延迟钾电导发展确定时间常数增加。描述延迟整流器膜电位依赖性的电压与n关系不受毒扁豆碱影响。得出的结论是，毒扁豆碱通过降低电压依赖性离子电导值并减慢其动力学，改变了动作电位的时间进程。讨论了从复杂药理效应的相平面分析获得的结果只能在一定限制条件下被接受。
