[Impact of loss of sympathetic innervation on peripheral nerve regeneration: an experimental study with rats].

Objective To investigate the impact of loss of sympathetic innervation on peripheral nerve regeneration. Methods Thirty-two SD rats underwent resection of the right middle cervical ganglion and excision and re-anastomosis of bilateral medium nerve, and then were randomly divided into 4 equal groups to undergo the following experiments. One, 2, 3, and 4 weeks later the sensory nerve action potentials (SNAPs) of bilateral medium nerves 5 mm from the anastomotic stoma and the compound muscle action potentials (CMAPs) of bilateral superficial digital flexor muscles were measured with stimulating and recording electrodes. Specimens of the distal part of bilateral medium nerves 5 mm from the anastomotic stoma were collected to calculate the number of medulated fibers by electron microscopy. The tendons of bilateral superior digital flexor muscles were cut ant the wrist, isolated to the terminal points, ligated, and connected to a sensor so as to record the maximum contraction power. The superior digital flexor muscle was completely resected to be weighted. Results CMAP failed to be recorded 1 week later. The wave amplitude of the nerve at the affected side increased along with time, however, the CMAP wave amplitudes of the affected side were all significantly lower than those of the healthy side (all P0.05). The SNAP wave amplitudes of the medium nerve of both sides increased along with the time. The SNAP levels 4 and 8 weeks later of the affected side were both lower than those of the healthy side (both P0.05). The number of medulated fibers of the medium nerve increased along with the time, however, the number of the affected side were significantly lower than those of the healthy side (all P0.05). Electron microscopy showed degeneration of medulla in bilateral medium nerves 1 week later, and newborn medulated fibers began to be seen since 2 weeks later. However, there were a greater number and more complete structure in the healthy side in comparison with the affected side. The wet weights of bilateral superior digital flexor muscles decreased 2 weeks later and then began to increase gradually. However, the wet weight 4 and 8 weeks later were significantly greater in the healthy side then in the affected side (both P0.05). Conclusion Resection of sympathetic nerve is advantageous on nerve regeneration.