DIFFERENTIAL EFFECTS OF TETRACAINE ON DELAYED POTASSIUM CHANNELS AND DISPLACEMENT CURRENTS IN FROG SKELETAL-MUSCLE
DIFFERENTIAL EFFECTS OF TETRACAINE ON DELAYED POTASSIUM CHANNELS AND DISPLACEMENT CURRENTS IN FROG SKELETAL-MUSCLE
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DOI：
10.1113/jphysiol.1976.sp011612
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发表时间：
1976-01-01
影响因子：
5.5
通讯作者：
ALMERS, W
中科院分区：
文献类型：
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作者：
ALMERS, W
用电压钳技术研究了延迟K+电流和位移电流。在正常的[Rana Temporaria]纤维中，延迟通道的电导在充分负电位时每3 mV增加e倍，在正电位时达到2-10m mho/cm2(平均5.8m-mho/cm2)的极限值。加入丁卡因(2 MM)可降低极限电导，使延迟通道的电压依赖性移至+25 mV，并使动力学减慢4倍。位移电流几乎不会被2 mM丁卡因改变。其电压依赖性漂移小于5 mV，其动力学不受影响。众所周知，四乙基铵离子(TEA)可以使延迟的K+通道的动力学减慢5倍，但不能像丁卡因一样改变位移电流的动力学。丁卡因和TEA对延迟通道的门控都有很大影响，但对位移电流的影响很小或没有影响。骨骼肌中的位移电流可能在很大程度上与延迟通道的开放和关闭无关。据估计，在肌肉中选通延迟通道可能需要不超过观察到的电荷位移的1%或2%。
Delayed K+-currents and displacement currents were studied with a voltage-clamp technique. In normal [Rana temporaria] fibers, the conductance of the delayed channel grows e-fold per 3 mV at sufficiently negative potentials and reaches a limiting value of 2-10 m mho/cm2 (mean 5.8 m-mho/cm2) at positive potentials. Adding tetracaine (2 mM) reduces the limiting conductance, shifts the voltage-dependence of the delayed channel to +25 mV more positive potentials and slows the kinetics 4-fold. The displacement currents are virtually unaltered by 2 mM tetracaine. Their voltage-dependence is shifted by less than 5 mV and their kinetics are unaffected. Tetraethylammonium ions (TEA) are known to slow the kinetics of delayed K+-channels 5-fold but fail, like tetracaine, to change the kinetics of the displacement currents. Both tetracaine and TEA have large effects on the gating of the the delayed channel, yet little or none on the displacement currents. The displacement currents in skeletal muscle probably are for the most part unrelated to the opening and closing of delayed channels. It is estimated that gating the delayed channel in muscle may require no more than 1 or 2% of the observed charge displacement.