Potassium conductance of the squid giant axon. Single-channel studies.
Potassium conductance of the squid giant axon. Single-channel studies.
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DOI：
10.1085/jgp.92.2.179
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发表时间：
1988-08
期刊：
影响因子：
--
通讯作者：
Bezanilla F
中科院分区：
文献类型：
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作者：
Llano I;Webb CK;Bezanilla F
采用膜片钳技术在鱿鱼巨大轴突上记录单个钾通道。我们提出的证据存在三种不同类型的渠道活动。在补丁，包含三到八个通道，合奏波动分析进行，以获得17.4 pS的单通道电导的估计。从这些多通道补丁获得的平均电流有一个激活的时间过程类似的宏观K电流记录灌注鱿鱼巨轴突。在可以记录单个事件的补丁中，可以找到电导为10，20和40 pS的通道。最常遇到的通道是20 pS通道;对于50 mV的脉冲，该通道打开的概率为0.9。在其他单通道贴片中，存在电导为40 pS的通道。该通道的活性因斑块而异。在某些贴片中，它显示出非常低的开放概率（对于50 mV的脉冲为0.16），并且在其激活时程中具有明显的滞后。在其他贴片中，40 pS通道开放的概率要高得多（在50 mV的保持电位下为0.75）。发现40-pS通道对K的选择性高于Na。在一些实验中，将切开的轴突暴露于不含K的溶液中几分钟。在此处理后，更频繁地观察到电导为10 pS的通道。我们的研究表明，宏观K电导是一个复合的几种类型的K通道，但每种类型的相对贡献还不清楚。20-pS通道激活的时间过程和仅通过将膜电位保持在正电位几秒钟使其难以激活的能力使得它可能是促成延迟整流器电导的主要通道。
The patch-clamp technique was implemented in the cut-open squid giant axon and used to record single K channels. We present evidence for the existence of three distinct types of channel activities. In patches that contained three to eight channels, ensemble fluctuation analysis was performed to obtain an estimate of 17.4 pS for the single-channel conductance. Averaged currents obtained from these multichannel patches had a time course of activation similar to that of macroscopic K currents recorded from perfused squid giant axons. In patches where single events could be recorded, it was possible to find channels with conductances of 10, 20, and 40 pS. The channel most frequently encountered was the 20-pS channel; for a pulse to 50 mV, this channel had a probability of being open of 0.9. In other single-channel patches, a channel with a conductance of 40 pS was present. The activity of this channel varied from patch to patch. In some patches, it showed a very low probability of being open (0.16 for a pulse to 50 mV) and had a pronounced lag in its activation time course. In other patches, the 40-pS channel had a much higher probability of being open (0.75 at a holding potential of 50 mV). The 40-pS channel was found to be quite selective for K over Na. In some experiments, the cut-open axon was exposed to a solution containing no K for several minutes. A channel with a conductance of 10 pS was more frequently observed after this treatment. Our study shows that the macroscopic K conductance is a composite of several K channel types, but the relative contribution of each type is not yet clear. The time course of activation of the 20-pS channel and the ability to render it refractory to activation only by holding the membrane potential at a positive potential for several seconds makes it likely that it is the predominant channel contributing to the delayed rectifier conductance.