OBJECTIVETo study on the analgesic mechanism of electroacupuncture (EA) in the rat of adjuvant arthritis (AA).

METHODSForty-eight SD rats were randomly divided into a blank control group (n = 8), an inflammatory group (n = 10), an acupoint EA group (n = 10), a non-acupoint EA group (n = 10) and a contralateral acupoint EA group (n = 10). Complete Freund's adjuvant (CFA) 50 microL were injected into the left malleolus' articular cavity in the rats except the blank control group for preparing single local adjuvant arthritis (AA) model. EA was given every other day to the acupoint EA group, the non-acupoint EA group and the contralateral acupoint EA group. The improving effects of EA at "Huantiao" (GB 30) and "Yanglingquan" (GB 34) on the dorsal flexion pain score and the swell of dorsum of hind paw were investigated, and effects of EA on Glial cell line-derived neurotrophic factor (GDNF) positive cells immunoreactivity in the inflammatory tissue of the AA rats on the 14th day after injection of adjuvant were observed with immunohistochemical technique.

RESULTSHyperalgesia and local swell, and GDNF in the dermal and subcutaneous tissue around the inflammatory ankle joint in the inflammatory groups were significantly higher than those in the blank control group. EA on the ipsilateral and contralateral acupoints reduced the pain, promoted the recovery of swell, and decreased the positive area percentage and mean optical density of GDNF positive cells in the dermal and the subcutaneous tissues. However, the non-acupoint EA group did not have this action.

CONCLUSIONEA can regulate expression of GDNF in local dermal tissue of the inflammatory focus in the AA rat, so as to exert the anti-inflammatory and analgesic effects.