Electroacupuncture combined with indomethacin enhances antihyperalgesia in inflammatory rats

Our previous study showed that electroacupuncture (EA), an adjuvant to conventional medicine, significantly attenuated hyperalgesia and inflammation. The present study is an evaluation of the potential synergism of EA and a subeffective dosage of indomethacin (INDO) in a rat model. Inflammation and hyperalgesia, manifesting as edema and decreased paw withdrawal latency (PWL) to a noxious stimulus, were induced by injecting complete Freund's adjuvant (CFA) subcutaneously into the plantar surface of one hind paw of the rat. EA treatments were given at acupoint GB30 immediately and 2 h post-CFA. INDO at 2 mg/kg was given (intraperitoneally) 40 min before the second EA. PWL and edema were measured prior to CFA and 2.5 and 5 h post-CFA. Ten and 100 Hz EA significantly inhibited CFA-induced hind paw hyperalgesia. Both low- and high-frequency EA combined with INDO enhanced antihyperalgesia compared to each component alone, and 10 Hz but not 100 Hz EA significantly reduced CFA-induced hind paw edema. A combination of low-frequency EA and INDO did not show synergistic inhibitory effects on edema. The results demonstrate that EA combined with INDO synergistically inhibits hyperalgesia and suggest an improved treatment strategy for inflammatory pain.