(A, B) Tail-withdrawal latencies in 46 °C water following topical capsaicin (0.4 mg/mL × 0.3mL) in vehicle (A,B)-, morphine 1.8 mg/kg (A)- and AT-121 0.03 mg/kg (B)- treated animals (n=6). (C, D) Tail withdrawal latencies in 50 °C before (BL) and after (Day 30) repeated administration of morphine (1.8 mg/kg, n=4) (C), or AT-121 (0.03 mg/kg, n=5) (D). Each data point represents mean ± SEM. Data were analyzed by two-way ANOVA with repeated measures, followed by Bonferroni’s multiple comparisons test. ∗p < 0.05, significantly different from the vehicle at 15 and 30 min. #p < 0.05, significantly different from BL values.