State-dependent hyperpolarization of voltage threshold enhances motoneurone excitability during fictive locomotion in the cat
State-dependent hyperpolarization of voltage threshold enhances motoneurone excitability during fictive locomotion in the cat
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DOI：
10.1111/j.1469-7793.2001.0271g.x
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发表时间：
2001-04-01
影响因子：
5.5
通讯作者：
McCrea, DA
中科院分区：
文献类型：
--
作者：
Krawitz, S;Fedirchuk, B;McCrea, DA
1.本实验在去脑成年猫上观察脑干诱发的虚构运动对后肢运动神经元动作电位起始阈电压（V-th）的影响。在控制和虚构的运动条件下，细胞内注射去极化斜坡电流或方波脉冲诱发的第一个尖峰的电压阈值的测量进行了比较。运动神经元的样本包括屈肌和伸肌运动神经元，以及具有低基强度电流和高基强度电流的运动神经元.在检查的所有38个运动神经元中，与对照条件相比，在虚构运动期间，动作电位在更多的超极化膜电位处启动（平均超极化-8.0 +/- 5.5 mV;范围-1.8至-26.6 mV）。V-th的超极化在虚拟运动开始时立即发生，并在运动活动终止后的几秒钟内（通常< 60 s）恢复。在运动过程中，无细胞内电流注入时自发出现的峰电位的V-th也降低.在没有运动的情况下，叠加有节奏的去极化电流脉冲在电流斜坡上并没有降低V-th到虚构运动期间所看到的程度。我们认为，V-th超极化的结果从一个尚未确定的神经调节过程中运行的运动，而不仅仅是运动过程中发生的膜电位振荡的结果。运动过程中动作电位起始的V-th超极化是运动神经元兴奋性的状态依赖性增加。这种V阶超极化可能是运动和其他运动任务中运动神经元活动产生的基本过程。
1. Experiments were conducted on decerebrate adult cats to examine the effect of brainstem-evoked fictive locomotion on the threshold voltage (V-th) at which action potentials were initiated in hindlimb motoneurones. Measurements of the voltage threshold of the first spike evoked by intracellular injection of depolarizing ramp currents or square pulses were compared during control and fictive locomotor conditions. The sample of motoneurones included flexor and extensor motoneurones, and motoneurons with low and high rheobase currents.2. In all 38 motoneurones examined, action potentials were initiated at more hyperpolarized membrane potentials during fictive locomotion than in control conditions (mean hyperpolarization -8.0 +/- 5.5 mV; range -1.8 to -26.6 mV). Hyperpolarization of V-th occurred immediately at the onset of fictive locomotion and recovered in seconds (typically < 60 s) following the termination of locomotor activity.3. The V-th of spikes occurring spontaneously without intracellular current injection was also reduced during locomotion.4. Superimposition of rhythmic depolarizing current pulses on current ramps in the absence of locomotion did not lower V-th to the extent seen during fictive locomotion. We suggest that V-th hyperpolarization results from an as yet undetermined neuromodulatory process operating during locomotion and is not simply the result of the oscillations in membrane potential occurring during locomotion. The hyperpolarization of V-th, for action potential initiation during locomotion is a state-dependent increase in motoneurone excitability. This V-th hyperpolarization may be a Fundamental process in the generation of motoneurone activity during locomotion and perhaps other motor tasks.