Fig. 8.
A85380 induces basal analgesia and enhances fentanyl-induced analgesia in adult rats. (A) Effects of A85380 (0.06 mg/kg, neck subcutaneously) on paw withdrawal latency in response to thermal stimuli, measured at 42 min after A85380 or saline with or without subsequent fentanyl administration (20 μg/kg more than 400 s intravenous [IV] infusion). (B) Effects of A85380 administration (0.06 mg/kg, neck subcutaneously) on the time spent engaging in nociceptive behaviors (licking and lifting) 20 to 40 min after formalin administration, measured at 32 to 52 min after A85380 or saline with or without subsequent fentanyl administration (20 μg/kg more than 400 s IV infusion). *P < 0.05, **P < 0.01, ***P < 0.001, statistically significant difference in compared groups, using one-way ANOVA (Holm–Sidak method). n = 8 animals each group.