OBJECTIVE In order to provide the scientific basis to find out a practical and effective method to evaluate the degree of muscle atrophy and a better method of prevention and treatment of skeletal muscle atrophy. METHODS Forty-two adult Spray-Dawley rats were used and the model of denervated gastrocnemius muscle was established by cutting off the tibial nerve. The muscle wet weight, diameter and cross section area of myocyte were measured. The motor end-plate, fibrillation potential amplitude and frequency of denervated skeletal muscle were observed. RESULTS The muscle wet weight rapidly reduced within 4 weeks. Afterwards, it maintained about 30 per cent of normal value, and the diameter and cross section area of myocyte progressively reduced. The motor end-plate slightly changed within 4 weeks, but its degeneration accelerated in 6 weeks and disappeared after 16 weeks. The fibrillation potential amplitude was maximum at 2 weeks and it progressively reduced after 12 weeks of muscle denervation. The changes of amplitude and frequency were consistent with the degeneration of end-plate. CONCLUSION The muscle wet weight, diameter and cross section area of myocyte, fibrillation potential amplitude and frequency could be considered as the morphological and electrophysiological indexes of muscle atrophy degree. It’s suggested that the repairing operation of peripheral nerve should be performed before the disappearance of motor end-plate.
To evaluate the value of clinical application of examination of fibrillation potential amplitude, 110 patients, 97 males and 13 females, were examined and only the maximum fibrillation potential amplitudes were recorded in 420 muscles. The results showed that there was no significant difference between sexes, ages and sides. However, significant difference was evident between the groups of different frequency (1+ to 4+). The fibrillation potential amplitude was maximum at 3 to 4 months after denervation and still remained at relatively high level for years in certain patients. No significant difference was showed between the time groups in incomplete nerve injuries. Surgery did not affect the course of fibrillation potential amplitude change. It was suggested that the muscle cells sustained their property for years after denervation in some patients, thus it might explain that satisfactory result could be obtained from operative repair in some late cases. The changes of fibrillation potential amplitude might indicate that the changes from muscle denervation was still reversible and might be more accurate than traditional method of examination.