Acetylcholine sensitivity and fibrillation potentials in electrically stimulated crush-denervated rat skeletal muscle

Juxtamuscular electrodes were implanted unilaterally in six groups of adult female Wistar rats to evaluate the effect of chronic electrical stimulation (ES) during denervation and reinnervation of the rat soleus muscle. Two weeks later, the animals underwent bilateral crush-denervation of the sciatic nerve at the sciatic notch. Six additional groups served as normal controls. The soleus muscles in the crush denervated and control groups were stimulated unilaterally with a 4mA, 4msec duration current given at 10Hz continuously 8 hours each day for 5, 10, 15, 20, 25 or 30 days. At the end of each period, the soleus muscles were evaluated for the muscle weights, acetylcholine (ACh) sensitivity and fibrillation potentials (FPs). The normal muscles were unaffected by the stimulation. The denervated-stimulated soleus muscles were heavier at 10 days (p less than 0.05) and had fewer FPs after 5 to 15 days (p less than 0.01) of electrical stimulation than their matched denervated controls. The ACh sensitivity throughout the experimental period and the fibrillatory activity from 20 to 30 days post-crush were similar in the denervated and the denervated-stimulated muscles. In conclusion, ES reduced the degree of atrophy and the number of fibrillations of the soleus muscle in the denervation stage. However, it neither enhanced nor impaired the reinnervation of muscle.