Fig. 8.
The effects of varenicline and ABT 594 on fentanyl-induced analgesia. After preadministration (neck subcutaneously, at 7 min before fentanyl) of saline, varenicline (1 mg/kg), ABT 594 (30 µg/kg), the effects of fentanyl administration (36 µg/kg over 10 min iv infusion) on the time (mean and SD) spent engaging in nociceptive behaviors (licking and lifting response of the injured paw to formalin injection) in the phase I and phase II (0 to 5 min, 20 to 40 minutes after formalin). Formalin (50 μl, 1.5% formalin diluted in saline) was injected into the intraplantar region of the right hind paw at 35 min after fentanyl. *P < 0.05, statistically significant difference compared with saline group, using one-way ANOVA (Holm–Sidak method). n = 8 animals for each group.