Mozhayeva G N, Naumov A P, Khodorov B I
Gen Physiol Biophys. 1986 Feb;5(1):17-46.
A further analysis of the effects of the steroidal alkaloid batrachotoxin (BTX) on sodium channels in frog node of Ranvier has been carried out under voltage-clamp conditions. The main properties of modified channels as compared with those of normal ones are as follows: The rate of channel closing is drastically decreased, whereas that of opening is changed slightly if at all; The steady-state voltage dependence of channel activation is shifted towards more negative potentials by 60-70 mV; Currents through modified channels do not show a decay during maintained depolarization as it is typical for normal channels. However modified channels retain the ability to partial inactivation as shown by experiments with depolarizing prepulses; Sodium against potassium selectivity beyond--20 mV suggesting either nonhomogeneity of the modified channels as for their kinetic and selectivity properties or potential-dependence of ionic selectivity for each channel; The selectivity sequence determined from peak current reversal potential measurements is as follows: H: Na :NH4:K = 528:1:0.47: :0.19; The effective pK value of proton block is decreased by about 0.4; 7) The sensitivity of the channels to tetrodotoxin (TTX) block is practically unchanged.
在电压钳条件下，对甾体生物碱箭毒蛙毒素（BTX）对蛙类朗飞氏结钠通道的影响进行了进一步分析。与正常通道相比，修饰通道的主要特性如下：通道关闭速率大幅降低，而开放速率即使有变化也很小；通道激活的稳态电压依赖性向更负电位偏移60 - 70 mV；通过修饰通道的电流在持续去极化期间不像正常通道那样出现衰减。然而，如去极化预脉冲实验所示，修饰通道保留了部分失活的能力；在-20 mV以下钠对钾的选择性，这表明修饰通道在动力学和选择性特性方面存在非均一性，或者每个通道的离子选择性具有电位依赖性；由峰值电流反转电位测量确定的选择性序列如下：H:Na:NH4:K = 528:1:0.47:0.19；质子阻断的有效pK值降低约0.4；7）通道对河豚毒素（TTX）阻断的敏感性实际上未改变。
