STUDIES ON FUNCTIONAL AND MORPHOLOGICAL CHANGES OF MECHANORECEPTOR IN ATROPHIC MUSCLE AFTER PASSIVE MOTION

本研究的目的是研究萎缩肌肉中骨骼肌机械感受器的反应性。研究了坡道拉伸和保持拉伸刺激下大鼠比目鱼肌机械感受器活性的变化。踝关节的被动运动诱导肌肉的斜拉和保持伸展。后肢悬吊或肌肉缩短位石膏固定2周后引起肌肉萎缩。悬吊和固定导致肌肉质量显著降低（p<0.05）。在斜坡拉伸过程中，健康肌肉机械感受器的放电频率呈线性函数。同样，机械感受器活性在悬空后肢中也表现为线性函数，但放电频率逐渐高于健康肢体。在固定后肢中，机械感受器放电频率呈指数函数。在保持伸展过程中，悬空和固定后肢的纺锤体传入反应的动态分量显著降低。然而，被动运动后这些肌肉的机械感受器传入反应得到改善。这些结果表明，经过2周后肢固定后肌肉萎缩，骨骼肌机械感受器的功能发生了变化。我们认为了解本体感觉敏感性的变化可以为萎缩性肌肉患者的康复治疗提供有用的线索。

The aim of the present study was to examine the responsiveness of skeletal muscle mechanoreceptors in atrophic muscle. The changes in mechanoreceptor activities during stimulation by ramp and hold stretching were studied in the rat soleus muscle with disuse atrophy. Ramp and hold stretching of the muscle was induced by passive motion of the ankle joint. Muscular atrophy was induced by hindlimb suspension or by immobilization with plaster cast at muscle shortening position for two weeks. The suspension and the immobilization resulted in a significant reduction of muscle weight (p<0.05). During the ramp stretching, the discharge frequency of the mechanoreceptors in healthy muscle showed a linear function. Similarly, the mechanoreceptor activities in the suspended hindlimb showed a linear function, but the discharge frequency rate became incrementally higher than in the healthy limb. In the immobilized hindlimb, the discharge frequency of the mechanoreceptors showed an exponential function. During hold stretching, the dynamic component of spindle afferent responses reduced significantly in the suspended and the immobilized hindlimbs. However, mechanoreceptor afferent responses were improved in these muscles after passive motion. These results indicate that following muscular atrophy achieved through two weeks of hindlimb immobilization, the function of the mechanoreceptors in skeletal muscle was changed. We suggest that awareness of changes of proprioceptive sensibility could provide a useful clue for advancing various therapeutic programs for rehabilitation of patients with atrophic muscles.