Histochemical Studies of the Reinnervation of Denervated Muscle by Direct Nerve Implantation in the Rat

In order to study whether some changes in denervated muscle fibers can be restored by nerve implantation, experiments were performed implanting the tibial nerve into the denervated (common peroneal nerve) tibialis anterior muscle in rats, with the wet weight of the muscle as well as the diameter and histochemical enzymatic activities of the muscle fibers being investigated during the duration of restoration after nerve implantation. The following results were obtained. 1) With time after deneravation, both the diameter of the muscle fibers and the wet weight of the muscle were decreased, and the activities of succinic dehydrogenase (SDH) and phosphorylase (PhR) in the fibers were markedly decreased. 2) Even after nerve implantation, the decrease in the wet weight of the muscle continued for 2 weeks. It was then followed by recovery to 86% of the control. No additional recovery was observed, however in further observation of from 10 to 15 weeks. 3) The diameter of red and white muscle fibers decreased until 4 weeks after nerve implantation, showing a tendency to recover gradually until 10 weeks after implantion. Further restoration, however, progressed only slightly up to 15 weeks. In addition, little difference in the diameters between the red and white muscle fibers could be observed. 4) The restoration of the SDH and PhR activities of the muscle fibers began at 4 weeks after nerve implantation and proceeded until 10 weeks after implantation. As to distribution types, two type-groups of muscle fibers with restored activities were observed ; one group consisting of fibers with equal enzymatic activities and the other consisting of ones showing a mosaic distribution. From the above results it was concluded that, in the rat, a direct implantation of the tibial nerve into the denervated muscle can cause a considerable restoration of some properties of the muscle fibers