To observe the difference of signaling afferent mechanism of acupoints analgesic effect between manual acupuncture (MA) and electroacupuncture (EA) of "Zusanli" (ST 36) in order to analyze the initiating mechanism of these two commonly used clinic acupuncture methods. A total of 64 SD rats were randomized into control, model, MA, EA, collagenase (type- I)-pretreatment (CP) + MA, CP + EA, disodium cromoglicate-pretreatment (DSCP) + MA and DSCP + EA groups with 8 cases in each. Arthritis model was established by intra-joint injection of complete Freunds' agent. MA(rotation, 20 min), and EA (21 min) were applied to bilateral "Zusanli" (ST 36) respectively in different groups. Pain threshold (PT, paw withdraw latency) was detected with 336 GT PAW/TAIL STIMULATOR and degranulated mast cells were counted under microscope separately. Compared with normal control group, PT values of model, MA, EA, CP + MA, CP + EA, DSCP + MA and DSCP + EA groups lowered significantly before treatment (P < 0.05). Comparison of the same one group showed that after the treatment, PT values of MA and EA groups increased considerably (P < 0.05). PT changing rates of CP + MA and DSCP + MA were significantly lower than that of MA group (P < 0.05), suggesting disappearance of MA analgesia (not EA analgesia) after lesion of collagen protein by CP in ST36 area. In comparison with control group, the degranulation ratios (DGR) of mast cells in MA and EA groups increased significantly (P < 0.05); while compared with MA and EA groups separately, DGR of the corresponding CP + MA and DSCP + MA, and CP + EA and DSCP + EA groups decreased markedly (P < 0.05), displaying an inhibition of mast cell degranulation following CP and DSCP in ST36 area. Both MA and EA can induce analgesia and concomitant increase of DGR of mast cells. The collagen fibers may contribute to MA initiated analgesic effect while the peripheral nerve receptors are probably involved in EA analgesia in rat.