Effects on paw withdrawal threshold of different frequencies of spinal cord stimulation (SCS) applied at 20–80% motor threshold in nerve-injured rats. (A) The paw withdrawal thresholds, shown as percent of prespinal nerve ligation (SNL) baseline, before and at different time points after SCS at one of three frequencies (50, 1 kHz, and 10 kHz) delivered at 20, 40, and 80% motor threshold (MoT, 0.024 ms, constant current, 30 min/session, 1 session/day). Data from animals that received sham stimulation in different studies were combined for analysis. Error bars are omitted to improve clarity. (B) On each treatment day, the overall effect of SCS on PWT was compared among groups by averaging together the PWTs at pre-SCS and 15, 30, and 60 min after the initiation of SCS applied at 20% MoT, 40% MoT, and 80% MoT. Data are expressed as mean + SEM in (B). +P < 0.05, ++P < 0.01, +++P < 0.001 versus pre-SCS PWT; *P < 0.05, **P < 0.01, ***P < 0.001 versus sham stimulation; †P < 0.05 versus 50 Hz.