Quantitative changes in cholinesterase activity of denervated sole plates following implantation of nerve into muscle

Abstract

Denervated muscle loses 60% of its sole-plate and background cholinesterase (ChE) activity within 1 week, and following nerve regeneration ChE is slowly restored. Since nerves implanted into denervated muscle form new cholinergic sole plates at the site of implantation, the present experiment was performed to determine whether implantation of nerve into denervated muscle would serve to restore ChE to the denervated (original) sole plates. In one group of rats the sternomastoid muscle was denervated; in another group this muscle was denervated and the hypoglossal nerve implanted into its rostral end. The ChE of the denervated sole plates was measured quantitatively at 1, 2, 4, and 8 weeks postoperatively. Both groups exhibited a 60% decrease in ChE 1 week postoperatively. In the denervated group, ChE decreased 10% more during the ensuing 7 weeks. However, in the group that received the nerve implantation, the ChE of the denervated sole plates began to increase after the second postoperative week and by 8 weeks was approximately double that of the denervated muscles. Histological preparations verified that the original sole plates remained denervated at this stage. It would appear that the presence of new myoneural junctions near the rostral end of the muscle served to partially restore ChE to the denervated sole plates in the mid-belly region of the muscle. We therefore conclude that in the adult rat a direct local connection between nerve and muscle is not necessary for the neurotrophic regulation of ChE at the sole plate.