Functional reorganization of the partially denervated hindlimb extensor and flexor muscle in rat.

In view of the neuromuscular system plasticity the functional changes induced by partial denervation are presented. The long-term effects of partial denervation of postural (soleus-SOL) or flexor (extensor digitorum longus-EDL) muscles on their EMG activity were studied in rats. The activity per motor unit was significantly higher both in the partially denervated SOL and EDL muscles. During standing or walking the EMG activity pattern of the partially denervated SOL muscle was similar to normal, while the partially denervated EDL muscle during standing exhibited abnormal tonic activity, and during locomotion its burst duration was strongly correlated to the step cycle duration. Thus, partial denervation led to an overall increase of activity of the remaining motor units in both SOL and EDL muscles, while the temporal pattern of muscle activity during locomotion was drastically altered in EDL muscle only, what indicates that partial denervation influenced the postural activity less than the phasic one.