After denervation, the skeletal muscles innervated by the nerve show neurogenic atrophy and the distal portion of the nerve show wallerian degeneration.
The purpose of this study is what the chronological changes are in the skeletal muscles and the distal portion of the nerve at 1wk, 2wks, 3wks, 4wks, 5wks, 7wks, and 9wks after sciatic nerve resection. Sciatic nerve resection, 0.5cm in length,
was
done
at just distal to the sciatic notch in adult Sprague Dawley male rat bilaterally. Histochemical study using NADH-tetrazolium reductase, SDH and myosin ATPase at pH 9.4 and electron microscopic study were conducted to observe and changes in muscle
fiber
types and plantaris muscles. And electron microscopic study for the muscle and the distal nerve was also done coincidentally. @EN The results were summerized as follows ;
@EN 1) The earliest change at 1 week after denervation was a few snake-coil fibers with nuclear internalization in muscle fibers, and it also showed ruffled sarcoplasmic membrane in some muscle fibers ultrastructurally.
2) Small angulated fibers appeared irregularly at 2 weeks after denervation but grouped atrophy of muscular bundles began at 3 weeks after denervation.
3) The gastrocnemius revealed earlier and severer atrophic changes than soleus and plantaris.
4) At 4 weeks after denervation, diffuse and marked rgouped atrophy was seen in gastrocnemius, soleus and plantaris. Thereafter the grouped atrophy was more generalized.
5) Degenerative changes in each type of muscle fiber showed irregular distribution but type 1 fibers were more frequently observed in the atrophic areas.
6) Mild axonal degeneration of the distal portion of the transected nerve appeared at 1 week after denervation but severe axonal degeneration with loss of axon and markedly hypertrophic Schwann's cells and macrophages showed at 2 week.
7) The phagocytic activity of macrophages and Schwann's cells decreased after fifth week but endoneurial collagen fibers were gradually increased.
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