Changes in sciatic nerve and spinal cord function induced by a CNS viral infection

Electrophysiologic response characteristics of mouse sciatic nerve and spinal cord were investigated following CNS infection with the temperature-sensitive (ts) vesicular stomatitis virus (VSV) mutant G31 KS5. Measurements were obtained before clinical symptoms of the virus-induced CNS disease appeared. Sciatic nerve peak conduction velocities were not different between virus and control inoculated groups. For all control groups, sciatic nerve response (SNR) recovery, characterized by the amplitude ratio of double pulse-evoked responses, followed a facilitation-depression time course. By 4 days after VSV inoculation, the time course of SNR recovery changed with the SNR amplitude ratios significantly depressed compared to control. Crossed spinal responses (CSRs) were measured from one sciatic nerve in response to stimulation of the contralateral sciatic nerve. For all control groups, CSR recovery, as characterized by area ratios calculated from single and double pulse evoked responses, followed a facilitation-depression time course. By 5 days after VSV inoculation, the time course of CSR recovery changed with the CSR area ratios significantly depressed compared to control. The results show that simple electrophysiologic techniques can be used to detect virus-induced changes in sciatic nerve and spinal cord previously undetectable by clinical measures.