The inner quaternary ammonium ion receptor in potassium channels of the node of Ranvier.
The inner quaternary ammonium ion receptor in potassium channels of the node of Ranvier.
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DOI：
10.1085/jgp.59.4.388
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发表时间：
1972-04
期刊：
影响因子：
--
通讯作者：
Hille B
中科院分区：
文献类型：
--
作者：
Armstrong CM;Hille B
通过从切断端扩散将季铵离子施加到单个有髓神经纤维的内部。在电压钳条件下研究了郎维叶结中钾通道的阻断。这些结果在几乎所有方面都与阿姆斯特朗对鱿鱼巨轴突的类似研究一致。当四乙基铵离子（TEA）、戊基三乙基铵离子（C5）或壬基三乙基铵离子（C9）位于结内时，去极化期间的钾电流开始以正常速率上升，达到峰值，然后再次福尔斯下降。这种不寻常的失活在C9中比在TEA中更完全。较大的去极化产生更多的阻滞。因此，在去极化期间，钾通道的阻断随着时间和电压而增长。阻滞随着复极化而逆转，但对于C9，在-75 mV下完全逆转需要数秒。逆转在120 mM KCl林格氏液中较快，在超极化至-125 mv期间较慢。所有这些作用与在郎维叶结上用外部季铵离子观察到的钾通道的时间和电压非依赖性阻断形成对比。外部TEA、C5和C9阻断，无灭活。外部的季铵离子受体似乎是不同的内部。显然，只有当钾通道的激活门打开时，才能到达内部季铵离子受体。我们认为，内部受体位于通道内，通道是一个孔，其激活门附近的轴质端。
Quaternary ammonium ions were applied to the inside of single myelinated nerve fibers by diffusion from a cut end. The resulting block of potassium channels in the node of Ranvier was studied under voltage-clamp conditions. The results agree in almost all respects with similar studies by Armstrong of squid giant axons. With tetraethylammonium ion (TEA), pentyltriethylammonium ion (C5), or nonyltriethylammonium ion (C9) inside the node, potassium current during a depolarization begins to rise at the normal rate, reaches a peak, and then falls again. This unusual inactivation is more complete with C9 than with TEA. Larger depolarizations give more block. Thus the block of potassium channels grows with time and voltage during a depolarization. The block reverses with repolarization, but for C9 full reversal takes seconds at -75 mv. The reversal is faster in 120 mM KCl Ringer's and slower during a hyperpolarization to -125 mv. All of these effects contrast with the time and voltage-independent block of potassium, channels seen with external quaternary ammonium ions on the node of Ranvier. External TEA, C5, and C9 block without inactivation. The external quaternary ammonium ion receptor appears to be distinct from the inner one. Apparently the inner quaternary ammonium ion receptor can be reached only when the activation gate for potassium channels is open. We suggest that the inner receptor lies within the channel and that the channel is a pore with its activation gate near the axoplasmic end.