Mechanisms of action potential propagation failure at sites of axon branching in the crayfish.
Mechanisms of action potential propagation failure at sites of axon branching in the crayfish.
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小龙虾轴突分支部位动作电位传播失败的机制。
DOI：
10.1113/jphysiol.1980.sp013202
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
Smith,DO
中科院分区：
文献类型：
--
作者：
Smith,DO
1.研究了小龙虾行走腿开启肌兴奋轴突重复刺激时导致动作电位传导阻滞的现象。 2. 用微电极在细胞外记录的动作电位在至少 3000 次脉冲后未能传播通过轴突分叉部位；降低速率或短暂停止刺激会导致传导恢复。 3. 故障最初发生在最外周的分支点，然后随着刺激的继续，故障发生在更中心的位置；阻滞位点的这种向心进展导致释放递质的突触末端数量逐步减少。 4.传导失败前，动作电位的传导速度和钠内向电流降低。 5、在块附近局部施加超极化电流或低[K+]生理盐水，可恢复传播；因此膜的去极化很可能导致失败。 6. 将制剂浸泡在代谢抑制剂 2,4-二硝基苯酚中长达 2 小时，对初始传导阻滞前的刺激脉冲数没有影响；然而，从故障中恢复所需的时间延长了。 7. 封闭前的脉冲次数与制剂的温度直接相关；计算出的 Q10 约为 1 。 3. 8. 表明在重复活动期间，跨膜的 K+ 梯度降低，导致去极化并最终导致传导失败。
1. The phenomena leading to action potential conduction block during repetitive stimulation of the excitor axon of the opener muscle in the crayfish walking leg were studied. 2. Action potentials, recorded extracellularly with micro‐electrodes, failed to propagate past sites of axonal bifurcation following at least 3000 impulses; reduction of the rate or brief cessation of stimulation resulted in restored conduction. 3. Failure occurred initially at branch points located most peripherally and then more centrally as stimulation continued; this centripetal progression of the site of block resulted in a stepwise reduction of the number of synaptic terminals from which transmitter was released. 4. Prior to conduction failure, the conduction velocity and the sodium inward current of the action potentials decreased. 5. Local application of hyperpolarizing current or of physiological saline with low [K+] in the vicinity of a block can restore propagation; thus depolarization of the membrane most probably causes failure. 6. Soaking the preparation for as long as 2 hr in the metabolic inhibitor 2,4‐dinitrophenol had no effect on the number of stimulus impulses before initial conduction block; however, the time required for recovery from the failure was prolonged. 7. The number of impulses prior to block was related directly to the temperature of the preparation; this had a Q10 calculated to be about 1 . 3. 8. It is suggested that during repetitive activity, the K+ gradient across the membrane is reduced, resulting in depolarization and eventually in conduction failure.
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