Effects of four herbal extracts on adjuvant-induced inflammation and hyperalgesia in rats

Objective: To evaluate the effects of four herbal medicine extracts on a ra t model of inflammatory hyperalgesia. Design/Interventions: Inflammation was induced by injecting complete Freund 's adjuvant (CFA) into one hindpaw of each rat. I;our herbs that are! routi nely prescribed in Traditional Chinese Medicine for treatment of pain were used: Duhuo (Radix Angelicae Pubescentis), gal jiang cao (Patriniae Herba c um Radice), Yan hu suo (Rhizoma Corydalis) and Sanqui (Panax Notoginseng). The crude water extracts of the herbs were inected intraperitoneally follow ing a repeated treatment profile. Outcome Measures: Thermal hyperalgesia was assessed by testing each rat's p aw withdrawal response to a noxious thermal stimulus. The magnitude of edem a was determined by measuring the maximal thickness of the paw with a calip er. The effect of herb extracts on motor performance was assessed by using an accelerating rotarod test. Result: Duhuo, Bai jiang cao, and Yan hu suo significantly attenuated CFA-i nduced hyperalgesia at 2 hours and facilitated the recovery from hyperalges ia (p < 0.05), when compared to saline-treated rats. The CFA-induced edema was reduced by Duhuo at 24 hours, 72 hours and 168 hours; Bai jiang cao at 24 hours, and Yan hu suo at 24 hours and 168 hours. Sanqi did not produce a ny significant effect on inflammation and hyperalgesia. The rotarod perform ance was slightly reduced by Bai jiang cao, Yan hu sue, and Sanqi (p < 0.05 ) but not by Duhuo treatment. Conclusion: The present study identified Duhuo as a selective and effective herbal agent in attenuating persistent hindpaw inflammation and hyperalges ia in rats. These results indicate that some herbal agents may provide an a lternative approach to the treatment of persistant inflammatory pain and hy peralgesia.