Influence of running exercise on γmotoneuron activity

很长一段时间以来，人们在经验上都知道，通过所谓的“训练”，重复有关的动作，可以完成身体表演。近年来，对训练引起的骨骼肌和神经肌肉连接的适应性变化进行了大量的科学分析研究。然而，关于中枢神经系统适应性变化的神经机制的报道很少。γ运动神经元-肌肉纺锤体系统通过其反馈回路调节肌肉的收缩，这对于建立精确的肌肉收缩的特殊和暂时控制所需要的物理性能是必不可少的。在目前的研究中,检查是否γmotoneuron-muscle主轴系统是影响体育锻炼,肌梭的传入响应末梢伸展的肌肉进行分析记录的放电活动Gia纤维从主结局以及GII比目鱼肌的肌肉纤维从次要结局的老鼠(TR)加载的时间间隔在跑步机上跑步40米/分钟的速度,并将训练大鼠与未训练大鼠（CR）进行比较。在主轴端部的每个传入响应中，通过检测各自的瞬时频率，测量拉伸结束时的峰值频率(P)、0.5秒后的静态频率和动态指数（DI）， P与S的差值。在GIa纤维上，TR中的P和DI明显大于CR，而在GII纤维上，TR中的P、S和DI明显大于CR。在GIa纤维中没有出现P降低而S增加的反应模式。结果表明，跑步运动可引起动态γ运动神经元活化等适应性变化。

It has been experietially well known for a long time that a physical performance can be accomplished by so-called 'training', repeating of the movement concerned. Recently, many studies have been reported on the scientific analysis of the training-induced adaptive changes in skeletal muscles and nueuromuscular junctions. However, there are a few reports on the neural mechanism for the adaptive changes induced in the central nervous system. γ motoneuron-muscle spindle system to modulate via its feed back circuit the contraction of the muscle could be essential for the establishment of the physical performance particularly required for an accurate special- and temporal-control of muscle contraction. In the present study, to examine whether or not γ motoneuron-muscle spindle system is influenced by physical training, the afferent responses of the muscle spindle endings to stretch of the muscle were analysed by recording the discharge activities of the Gia fibers from the primary endings as well as the GII fibers from the secondary endings in the soleus muscles of the rats (TR) which were loaded by the interval running on a treadmill at the speed of 40 m/min, and a comparison was made between trained rats and untrained rats (CR). In each afferent response of the spindle ending, peak frequency (P) at the end of stretch, static frequency 0.5 sec later and the dynamic index (DI), the difference between P and S were measured by detecting the respective instantaneous frequency. It was found that on the GIa fibers P and DI in TR were significantly greater than those in CR while on the GII fibers P, S and DI in TR than those in CR. No response pattern such a decreased P accompanied by an increased S in the GIa fiber was encountered. The results suggest that the adaptive changes such as the activated dynamic γ motoneuron are induced by running exercise.