Effects of intrathecal injection (arrow) of anti-BDNF antibody (20 μg, closed circles) or normal sheep IgG (20 μg, open circles) on paw withdrawal response to noxious heat of the rats that received L5 SPNL. Difference scores were calculated by subtracting contralateral withdrawal latencies from ipsilateral withdrawal latencies and expressed as mean ± SEM (n = 8 for each treatment). Thermal hyperalgesia was abolished for at least 2.5 hr by anti-BDNF antibody injection, whereas normal sheep IgG injection had no significant effect on the behavior. *p < 0.05 versus before L5 SPNL (pre ope); #p < 0.05 versus before injection (pre inj.) by one-way ANOVA followed by Fisher's PLSD.