Pain relief is a puzzle in the human medical history to fight against diseases.Though no possible single theory can clarify the mechanism of acupuncture analgesia,it is the most acceptant treatment clinically and basically.In normal,acute pain and partial chronic constriction injury chronic pain rats,as well as in healthy and chronic sciatica patients,we studies the effect of acupuncture on inhibition of C-fiber reflex or RⅢ reflex as a quantitative sensory test for acute pain or chronic pain to investigate the mechanism of acupuncture analgesia.The results showed acupuncture stimulation with intensity to excite A-fiber can provoke apparent homotopic analgesia,whereas stimulation to activate Aδ- or C-fiber improves the whole body threshold.Homotopic acupuncture is mediated by gate control pathway,whereas heterotopic benefits from excitation of mesencephalic structure and the participation of diffuse noxious inhibitory controls (DNIC).We also tested that in chronic pain patients or animals models,DNIC were impaired functionally,leading to heterotopic acupuncture analgesia being weakened.Our research demonstrated that acupuncture on acute and chronic pain may be mediated differently by gate control and DNIC,according to location of acupoint,stimulation and pain modality.