Fig. 2. Conditioning stimulation intensity was determined by recording the antidromic sciatic compound action potential. (A ) Sciatic compound action potentials evoked by dorsal root stimulation usually revealed two distinct groups of waves corresponding to Aα/β and Aδ fiber activation. The Aδ component to dorsal column stimulation is often hard to differentiate or missing. (B ) The areas under the Aα/β and Aδ curves/waveforms in response to 3.0-mA stimulation at the dorsal column and the dorsal roots were plotted. Data are expressed as mean ± SEM. *P < 0.05. **P < 0.01 vs. sham-operated group. †P < 0.05 versus day 14–16 post–spinal nerve ligation. (C ) The Aα/β plateau for each stimulation site was plotted. Data are expressed as mean ± SEM. *P < 0.05 versus sham-surgery group. #P < 0.05. ##P < 0.01 versus dorsal root stimulation. (D ) The ipsilateral paw withdrawal threshold was significantly decreased from preinjury baseline at day 5 postinjury and 2–3 days before the electrophysiologic recording dates (prerecord). Data are expressed as median.*P < 0.05. **P < 0.01 versus corresponding preinjury baseline. Ab-pl = Aα/β plateau, the lowest stimulus intensity that evokes a peak Aα/β component without inducing an Aδ component; Ab-th = Aα/β threshold; Ad-th = Aδ threshold.