Effects of U-50488 (2 mg/kg i.p.) repeated treatment alone or in combination with nor-BNI (20 mg/kg i.p.), AM251 (1 mg/kg i.p.) or AM630 (mg/kg i.p.) on mechanical withdrawal threshold of the the ipsi- (A) and contralateral (B) hind-paw 3 and 7 days after formalin injection in mouse. Data were expressed as mean ± S.E.M of mechanical withdrawal thresholds in grams. # indicate significant differences vs veh/saline treated mice, * indicate significant differences vs vehicle treatment in formalin injected mice and ° indicate significant differences vs U-50488 /formalin injected mice. P values <0.05 were considered statistically significant (one-way ANOVA followed by Student-Newman Keuls).