Conclusions
Conventional SCS and 1200 Hz, low-intensity SCS modestly attenuated below-level mechanical hypersensitivity after SCI. Inhibition of WDR neurons was not associated with pain inhibition from conventional SCS.
Methods
Male rats underwent a moderate contusive injury at the T9 vertebral level. Six to eight weeks later, SCS or sham stimulation (120 min, n = 10) was delivered through epidural miniature electrodes placed at upper-lumbar spinal cord, with using a crossover design. Mechanical hypersensitivity was examined in awake rats by measuring paw withdrawal threshold (PWT) to stimulation with von Frey filaments. WDR neurons were recorded with in vivo electrophysiologic methods in a separate study of anesthetized rats.
Results
Both conventional SCS and 1200 Hz SCS increased PWTs from prestimulation level in SCI rats, but the effects were modest and short-lived. Sham SCS was not effective. Conventional SCS (10 min) at an intensity that evokes the peak Aα/β waveform of sciatic compound action potential did not inhibit WDR neuronal responses (n = 19) to graded or repeated electrical stimulation that induces windup. Conclusions: Conventional SCS and 1200 Hz, low-intensity SCS modestly attenuated below-level mechanical hypersensitivity after SCI. Inhibition of WDR neurons was not associated with pain inhibition from conventional SCS.