FAST AND SLOW STEPS IN THE ACTIVATION OF SODIUM-CHANNELS
FAST AND SLOW STEPS IN THE ACTIVATION OF SODIUM-CHANNELS
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DOI：
10.1085/jgp.74.6.691
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发表时间：
1979-01-01
影响因子：
3.8
通讯作者：
GILLY, WF
中科院分区：
文献类型：
--
作者：
ARMSTRONG, CM;GILLY, WF
本文研究了电压钳位、内灌流鱿鱼[Loligo pealei]轴突钠电导（gNa）和相关门控电流（IG）的动力学特征。继一个步骤去极化IG ON有几个动力学组件：一个快速，早期阶段，主要是在gNa打开;延迟的中间组件开发的gNa增加;和缓慢的组件后，继续gNa被完全激活。对于小的去极化，早期显示快速上升（< 40 μ s）和平滑衰减;慢分量不可检测。在大脉冲期间，所有3个分量都存在，并且最早的分量示出持续约的上升阶段或初始平台。80 μ s。IG的稳态和动力学特征受控制脉冲电流的影响最小，只要控制被限制在足够负的电压范围内。强短脉冲后的IG OFF也显示上升阶段。产生gNa失活和IG固定的去极化预脉冲消除了IG OFF的上升相。gNa、IG ON的固定部分和上升相在不同复极化周期后用第二次去极化脉冲测试时以相似的时间过程重新出现。30 mM外部ZnCl 2延迟并减慢gNa激活，抑制上升相，并减慢IG ON的随后衰减。当通道关闭时，Zn不影响gNa尾部或IG OFF的动力学。一个连续的动力学模型的Na通道激活，充分描述的意见。IG ON的快速早期阶段是由一系列几个快速步骤产生的，而中间组分反映了随后的步骤。慢分量太慢而不能与gNa活化明确相关。
Kinetic features of Na conductance (gNa) and associated gating current (Ig) were studied in voltage-clamped, internally perfused squid [Loligo pealei] axons. Following a step depolarization Ig ON has several kinetic components: a rapid, early phase largely preceding gNa turn-on; a delayed intermediate component developing as gNa increases; and a slow component continuing after gNa is fully activated. With small depolarizations the early phase shows a quick rise (< 40 .mu.s) and smooth decay; the slow component is not detectable. During large pulses all 3 components are present, and the earliest shows a rising phase or initial plateau lasting .apprx. 80 .mu.s. Steady-state and kinetic features of Ig are minimally influenced by control pulse currents, provided controls are restricted to a sufficiently negative voltage range. Ig OFF following a strong brief pulse also shows a rising phase. A depolarizing prepulse producing gNa inactivation and Ig immobilization eliminates the rising phase of Ig OFF. gNa, the immobilized portion of Ig ON, and the rising phase reappear with similar time-courses when tested with a second depolarizing pulse after varying periods of repolarization. 30 mM external ZnCl2 delays and slows gNa activation, prolongs the rising phase, and slows the subsequent decay of Ig ON. Zn does not affect the kinetics of gNa tails or Ig OFF as channels close. A sequential kinetic model of Na channel activation, which adequately describes the observations is presented. The rapid early phase of Ig ON is generated by a series of several fast steps, while the intermediate component reflects a subsequent step. The slow component is too slow to be clearly associated with gNa activation.