Effects of Peripheral Neuropathy on CTB-labeled Motor Neurons Following Ligation of the Tibial Nerve

Changes in CTB labeled motor neurons of the spinal cord were observed after the induction of peripheral neuropathy by ligation of the tibial nerve. Rats were anesthetized and the tibial nerve was ligated with 3-0 silk. The rats were separated into three groups based on the length of time the tibial nerve was ligated (1, 2, or 4 weeks). After the ligation procedures were complete, the tibial nerve stumps were soaked in CTB solution. Tibial nerve segments and the spinal cord were then observed. In the control and experimental groups, CTB-labeled neurons formed a discrete population that was concentrated primarily at the L5 level, while the contributions from L4 and L6 were minor. According to the distributions, CTBlabeled neurons were divided into rostral and caudal groups. A selective decrease of CTB-labeled neurons was observed only in the caudal group, extending from the rostral L5 to one-half of the rostral L6. The total numbers of CTB-labeled motor neurons were 2,160±169.3, 1,002±245.1, 587.5±346.5, and 1,728±402.6 in the control group, 1 week group, 2 week group, and 4 week group, respectively. The selective decrease of CTB-labeled neurons in the caudal division was responsible for the decrease in the total number of labeled neurons in all groups. Following peripheral neuropathy caused by ligation of the tibial nerve, CTB-labeled neurons in the spinal cord decreased selectively. These results may provide important neuroanatomical data regarding the effects of peripheral neuropathy by ligation of the tibial nerve.