von Frey hair algesiometry in mice with acute joint inflammation. (A) Time course of the effects of URB597 (3.0 mg/kg) on inflamed hindlimb von Frey withdrawal threshold. URB597 significantly improved hindlimb withdrawal thresholds when compared to vehicle. P <0.0001; two-way ANOVA; n =12 to 14. (B) Inflammation-induced secondary allodynia 60 minutes after local administration of URB597 (3.0 mg/kg), as tested by von Frey hair algesiometry. URB597 significantly improved mechanosensitivity. This effect was blocked by AM251 (0.2 mg/kg), but not AM630 (0.2 mg/kg). Contralateral administration of URB597 had a negligible effect on ipsilateral tactile sensitivity. Data are means ± SEM. *P <0.05, **P <0.01; one-way ANOVA with Bonferroni's post hoc test; n = 9 to 14. ANOVA, analysis of variance; SEM, standard error of the mean.