Adult-Age Inflammatory Pain Experience Enhances Long-Term Pain Vigilance in Rats
Figure 2
Effect of chronic pain history on formalin pain.
(A) The time course of CFA-induced thermal hyperalgesia. A significant decrease was observed in PWL of the CFA-injected paw starting at day 1 and persisting at least 14 days, compared with baseline and saline control. Morphine treatment over day 0–3 prevented CFA-induced hyperalgesia. (B) Time-effect curve of chronic pain experience on formalin-induced spontaneous pain behaviors. Compared with NS and CFA+MOR rats, licking behaviors in CFA-treated rats were significantly enhanced in phase II (11–60 min), but not phase I (0–10 min). (C) Cumulative licking time in the formalin test. CFA: complete Freund's adjuvant; NS: normal saline; MOR: morphine. *, **, ***: P<0.05, P<0.01, and P<0.001, respectively, compared with the NS group. #, ##, and ###, P<0.05, P<0.01, and P<0.001, respectively, compared with the CFA+MOR group.