Electrical stimulation effect on denervated skeletal myofibers in rats: a light and electron microscopic study

The purpose of the present study was to determine morphologically the effect of electrical stimulation on denervated rat extensor digitorum longus (EDL) muscle. Fifteen adult male rats were divided in to 3 groups: control, denervated-nonstimulated, and denervated-stimulated. Electrical stimulation treatment (1 hr/day for 24 days) began 4 days postsurgery. All animals were sacrificed 28 days after surgery; the EDL muscle was fixed in situ, removed, and processed for light and electron microscopic examination. Fibers from sections taken from the middle third of the muscle were differentiated into types I and II; fiber diameters were obtained and compared for each experimental group. Although both types atrophied following denervation, type I atrophied to a lesser extent than type II. Electrical stimulation was beneficial in retarding denervation atrophy for both types. Membrane-glycogen complexes were found on electron microscopy to be in high proportion in type II stimulated fibers but were observed infrequently in denervated nonstimulated muscles and were not apparent in control muscles. These glycogen arrays may be expressions of sarcoplasmic reticulum anabolic functions, indicating a high degree of regenerative metabolic activity in treated fibers. This study indicates that electrical stimulation as a method to induce muscle activity, can retard denervation atrophy.