Figure 6.

Both NGF/GFP- and NGF/Sema3A-induced axon regeneration leads to near complete functional recovery of thermal nociception. PWL was measured on both right and left hindlimbs before and once a week after injury and treatment. The ratios of right (experimental) and left (control) hindpaw latencies were compared to examine the influence of different treatments on nociceptive functions. A, L4, L5 dorsal root injury caused an immediate loss of paw withdrawal response, raising the ipsilateral PWL to the cutoff value. No spontaneous recovery of PWL was found in GFP/Ad-treated rats. NGF/GFP and NGF/Sema3A treatments induced recovery of nociceptive function and decreased PWL to near-normal levels by the end of the study. There is no significant difference in PWL between these two groups throughout the observation time. PWL recovery disappeared after relesioning the L4 and L5 dorsal roots in either NGF+GFP/Ad- or NGF+Sema3A/Ad-treated rats (B), indicating that the recovery was attributed to regenerating sensory axons and not axon sprouting. Values represent mean ± SD; n = 5–6. *p < 0.05, **p < 0.01, analyzed by two-way ANOVA.