The Effect of Denervation and Subsequent Reinnervation on the Morphology of Rat Soleus Muscles.

Abstract

Abstract.To investigate the effect of denervation and subsequent reinnervation on skeletal muscle, a histochemical study was performed on the soleus muscles of rats. Partial denervation was carried out by freezing the sciatic nerve locally, and the change in the nerve and the soleus muscles was examined for 5 weeks. The muscle fiber cross-sectional area of the denervated soleus muscles progressively declined to a minimum 2 weeks after the injury (type I fibers, 1209.1 ± 248.3 µm 2 ; type II fibers, 802.4 ± 126.8 µm 2 ) and began to reverse the decline at 3 weeks. The type II fiber ratios to total fiber of the denervated sides were consistently higher than the control levels, and muscle fibers stained in both acid preincubation and alkaline preincubation were observed. The proportion of type II fibers in the soleus muscles showed an increase and consequently a decrease with a short delay in response to denervation and consequent reinnervation. These data suggest that denervation elicits an alteration in fiber type composition and a reduction in fiber size. The increase of type II fibers seemed to occur in hybrid fibers containing both myosin heavy chains I and II at varying ratios in the same fibers. The reinnervation took the crucial role of recovering from atrophy and composing the integrity of the soleus muscles. However, the ability to generate muscle tension needs a much longer time to recover. This suggests a need to investigate interventions to facilitate the functional recovery of partially-denervated muscle.

Effect of Extracorporeal Shock Wave Therapy on Denervation Atrophy and Function Caused by Sciatic Nerve Injury

“…Sunderland15 ) , in a study of muscle atrophy resulting from crush injury administered to rats, reported that the weight of the gastrocnemius and soleus muscles and the cross-sectional areas of muscle fibers decreased significantly with time. Sakakima et al found that, after two weeks of nerve injury, the affected side showed the highest degree of muscle atrophy16 ) .…”

Effect of Exercise Training after Partial Denervation in Rat Soleus Muscles

“…The results were considered attributable to increased protein synthesis following mechanical stimulation through exercise training and to an increase in motor units due to sprouting nerve fibers 6,10,17) . The proportion of type II fiber to total muscle fibers is reportedly increased following denervation 18,19) . However, the present study found no change in muscle fiber-type ratios.…”

Eletroestimulação seletiva mantem estrutura e função do tibial anterior desnervado de ratos

“…14 The main alteration undergone by the denervated skeletal muscle was disuse atrophy. 15 It was one of the main justifications for the use of electrical stimulation in these cases, for its prevention. [16][17][18] The reduction in the area of the muscle fibers after denervation was observed in this study only in the denervated groups and was compatible with the findings in literature.…”

“…Several studies reported a significant reduction of the cross section area of the muscle fibers in the first two weeks after denervation. 15 They considered that at the end of the three weeks after this procedure, there was a reduction of 80% of the area of the muscle fibers when compared with normal fibers. 19 The role of electrical stimulation in the delay and/or prevention of atrophy of the denervated muscle was the subject of countless publications.…”