Different voltage-dependent potassium conductances regulate action potential repolarization and excitability in frog myelinated axon
Different voltage-dependent potassium conductances regulate action potential repolarization and excitability in frog myelinated axon
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不同电压依赖性钾电导调节青蛙有髓轴突的动作电位复极化和兴奋性
DOI：
10.1016/0306-4522(95)00139-a
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发表时间：
1995
期刊：
影响因子：
3.3
通讯作者：
A. Padjen
中科院分区：
文献类型：
--
作者：
M. Poulter;A. Padjen
细胞内微电极记录检测了钾通道阻滞剂4-氨基吡啶（gKf1、gKf2、13的选择性阻滞剂）和四乙基铵（gKf1、gKf2和gKf2、13的阻滞剂）对青蛙大髓鞘轴突重复活动的影响。阻滞剂通过从含有4-氨基吡啶或4-氨基吡啶和四乙基铵的混合物的记录微电极扩散泄漏的方法应用于细胞内。在轴突插入后5分钟内，测量钾电导阻滞的向外整流明显减少。在30分钟内观察到80%的最大阻断在延长的记录会话（bbb10 1小时）。与电阻增加并行，动作电位持续时间增加（最多5毫秒）。这归因于gKf2的阻滞。兴奋性有规律地增加，表现为动作电位序列（调节能力下降），最长持续200 ms（分别为54±8 vs 111±22,4-氨基吡啶vs 4-氨基吡啶-四乙基铵，n = 8和6，P < 0.006）。微电极中4-氨基吡啶-四乙基铵的存在降低了单独用4-氨基吡啶处理的纤维的峰值频率适应性（每个峰值间隔数的瞬时动作电位频率）（32±9 vs 7±1 Hz； 4-氨基吡啶vs 4-氨基吡啶-四乙基铵，n = 8和6，P < 0.04）。这种效应是由于四乙基铵阻滞了gks。这些结果表明，髓鞘轴突重复活动的两个方面受不同钾电导的调节：gkf2调节早期调节和动作电位复极化，而gkf2调节晚期调节和尖峰频率适应。
Intracellular microelectrode recordings were used to examine the effects of the potassium channel blockers: 4-aminopyridine, a selective blocker of fast potassium conductances gKf1and gKf2,13and tetraethylammonium, a blocker of gKf1, gKf2and the slow conductance gKs,13on the repetitive activity of large myelinated axons of frog. The blockers were applied intracellularly by diffusional leak of the agents from the recording microelectrode containing either 4-aminopyridine or a mixture of 4-aminopyridine and tetraethylammonium. A decrease in outward rectification, a measure of the block of the potassium conductances, was evident within 5 min of axon impalement. Within 30 min 80% of maximal blockade was observed during prolonged recording sessions (> 1 h). Parallel with the resistance increase, the action potential duration increased (up to 5 ms). This was attributed to the block of gKf2. The excitability regularly increased, manifested as a train of action potentials (a decrease in accomodation) for a maximum of 200 ms (54 ± 8 vs 111 ± 22, 4-aminopyridine vs 4-aminopyridine-tetraethylammonium, respectively, n = 8 and 6, P < 0.006). The presence of 4-aminopyridine-tetraethylammonium in the microelectrodes decreased the spike frequency adaptation (the instantaneous action potential frequency per spike interval number) observed in fibres treated with 4-aminopyridine alone (32 ± 9 vs 7 ± 1 Hz; 4-aminopyridine vs 4-aminopyridine-tetraethylammonium, n = 8 and 6, P < 0.04). This effect was attributed to block of gKsby the tetraethylammonium. These results suggest that the two aspects of repetitive activity in myelinated axons are regulated by different potassium conductances: gKf2modulates the early phase of accomodation and action potential repolarization, whereas gKsregulates the late phase of accomodation and the spike frequency adaptation.
影响因子：
2.5
作者：
P. Schwindt;W. J. Spain;W. Crill
通讯作者：
P. Schwindt;W. J. Spain;W. Crill