The effect of electrical stimulation on reinnervation of rat muscle: contractile properties and endplate morphometry.

Denervated extensor digitorum longus muscles of Wistar rats were electrically stimulated in vivo for 4 days (2h per day) after peroneal nerve crush 1 cm from the muscle. Isometric contractile properties and endplate ultrastructure were measured on days 11 and 18. On day 11, the time to peak (116% of control) and 1/2-relaxation time (136% of control) for the twitch tensions of stimulated muscles measured in vivo were significantly less than those (127% and 157% of controls, respectively) of non-stimulated muscles. Peak twitch and tetanic tensions were not significantly different. The postsynaptic area of endplates for stimulated muscles were closer in size to controls than those for the non-stimulated ones. On day 18, no difference was found in the contractile responses between stimulated and non-stimulated groups. Similarly, the postsynaptic areas were the same for both groups. These results demonstrate that denervated muscle stimulated electrically for 4 days prior to reinnervation can preserve the structure of the endplate as well as accelerate recovery of normal function in reinnervated muscle fibers after 11 days of denervation.