Fig. 5

TNF-α exacerbated acid-induced nociceptive behaviors in rats. Nociceptive responses were evoked by intraplantar injection of acetic acid (1%, 50 μl) in rats in the presence of the TRPV1 inhibitor AMG9810 (10 μM). Intraplantar pretreatment of TNF-α (1, 3, and 10 ng) dose-dependently increased the number of acid-induced flinching. TNF-α (10 ng) exacerbating effect on nociceptive behaviors was reversed by intraplantar co-treatment of p38 MAPK inhibitor SB202190 (25 μM). Rats (10 ng TNF-α contral group) injected with acetic acid into one hind paw and TNF-α (10 ng) into the contralateral hind paw displayed similar nociceptive behaviors to those seen in control rats. Each bar represents the number of flinches that animals spent licking/lifting the injected paw during first 5-min observation period. *P < 0.05, **P < 0.01, one-way ANOVA followed by post hoc Bonferroni’s test, compared with control column; # P < 0.05, one-way ANOVA followed by post hoc Bonferroni’s test, compared with 10 ng TNF-α column. Each group represents the mean ± S.E.M. of 10 rats