Objective:To elucidate the underlying neuroimmunological mechanism of the effect of EA in resisting inflammatory pain. Methods:21 Wistar rats were evenly randomized into control

inflammation and electroacupuncture (EA) groups. Focal inflammation was produced by subcutaneous injection of 5% formalin (50?μL) into the rats' hindpaw. EA (4～16?Hz

1～3?V) was applied to “Huantiao”( GB 30) and “Yanglingquan” (GB 34) for 30?min. Spontaneous pain related response(flinching and lifting/licking the affected hindpaw)

inflammatory reaction

the substance P (SP) and Interleukin (IL) 1β positive immunoreaction (IR) cells of the epidermis

dermis and hypodermis of the focal tissue were observed with behavioral measures and immunohistochemical techniques separately. Results: EA significantly reduced spontaneous pain related responses in focal inflammatory rats( P <0 01). The total number of inflammatory cells (per 100×100?μm 2 section) in EA group was significantly lower than that of inflammation group

suggesting an anti inflammatory effect. The integral optical density values of the SP IR and IL 1β IR positive cells in the focus were significantly higher than those of control group

whereas those of the two types of IR positive cells were considerably lower than those of inflammation group( P <0.01)

suggesting that EA may resist inflammation and pain by suppressing the synthesis and release of SP from the focal sensory nerve endings

reducing the migration of immunocytes to the focus and lessening the synthesis and release of IL 1β.Conclusion: SP and IL 1β participate in the process of inflammatory pain induced by formalin

and EA may relieve focal inflammatory pain by reducing SP and IL 1β levels.