Armstrong C M, Bezanilla F
J Gen Physiol. 1974 May;63(5):533-52. doi: 10.1085/jgp.63.5.533.
The sodium current (I(Na)) that develops after step depolarization of a voltage clamped squid axon is preceded by a transient outward current that is closely associated with the opening of the activation gates of the Na pores. This "gating current" is best seen when permeant ions (Na and K) are replaced by relatively impermeant ones, and when the linear portion of capacitative current is eliminated by adding current from positive steps to that from exactly equal negative ones. During opening of the Na pores gating current is outward, and as the pores close there is an inward tail of current that decays with approximately the same time-course as I(Na) recorded in Na-containing medium. Both outward and inward gating current are unaffected by tetrodotoxin (TTX). Gating current is capacitative in origin, the result of relatively slow reorientation of charged or dipolar molecules in a suddenly altered membrane field. Close association with the Na activation process is clear from the time-course of gating current, and from the fact that three procedures that reversibly block I(Na) also block gating current: internal perfusion with Zn(2+), prolonged depolarization of the membrane, and inactivation of I(Na) with a short positive prepulse.
在电压钳制的枪乌贼轴突进行阶跃去极化后产生的钠电流（I(Na)）之前，存在一个短暂的外向电流，该电流与钠通道激活门的开放密切相关。当通透离子（Na和K）被相对不通透的离子取代时，以及当通过将正向阶跃电流与完全相等的负向阶跃电流相加来消除电容性电流的线性部分时，这种“门控电流”最容易被观察到。在钠通道开放期间，门控电流是外向的，并且当通道关闭时，存在一个内向的电流尾，其衰减的时间进程与在含钠介质中记录的I(Na)大致相同。外向和内向门控电流均不受河豚毒素（TTX）的影响。门控电流起源于电容，是带电或偶极分子在突然改变的膜电场中相对缓慢重新定向的结果。从门控电流的时间进程以及以下三个事实可以清楚地看出它与钠激活过程密切相关：用Zn(2+)进行内部灌注、膜的长时间去极化以及用短暂的正向预脉冲使I(Na)失活，这三种方法均可逆地阻断I(Na)，同时也阻断门控电流。
