Electroacupuncture and transcutaneous electrical acupoint stimulation with different intensities relieve muscular of inflammatory pain of the rats

Abstract

To observe and compare the ameliorate effects of electroacupuncture (EA) and transcutaneous electrical acupoint stimulation (TEAS) with different intensities on inflammatory muscle pain, so as to confirm the role of different afferent nerve fibers in different layers (skin or muscle) in pain relief of acupuncture. The intensities of the thresholds of A (Ta) and C (Tc) were selected for TEAS and EA. TEAS and EA were applied on the layer of skin and muscle of "Liangqiu" (ST34), respectively. Forty-eight rats were randomly divided into control, model, TEAS-Ta, TEAS-Tc, EA-Ta and EA-Tc groups (n=8 in each group). The inflammatory muscle pain model was established by complete Freund's adjuvant (CFA) injection into the right biceps femoris muscle. EA or TEAS was applied once a day for 3 days. The weight difference between the hind limbs and the abnormal electromyography (EMG) activities were observed as an index for pain of the rats. After modeling, the weight difference between the hind limbs was increased markedly in the model group relevant to the control group (P<0.01). Compared with the model group, the weight difference between the hind limbs in the TEAS-Tc, EA-Ta, and EA-Tc groups was significantly decreased (P<0.05, P<0.01). Compared with that before intervention, the area under the curve and discharge frequency of abnormal EMG of rats in the TEAS-Tc and EA-Ta groups were significantly reduced after intervention (P<0.01, P<0.05), while those in the EA-Tc group were significantly increased (P<0.05). After the intervention, compared with the TEAS-Ta group, the inhibition rate of the area under the curve and the discharge frequency of the abnormal EMG in the TEAS-Tc group increased significantly (P＜0.05); and those were also increased in the EA-Ta group when compared with the EA-Tc group (P<0.01). TEAS with Tc or EA with Ta in the muscle layer can alleviate the pain and inhibit the abnormal EMG in inflammatory muscle pain rats. It is indicated that local pain relief by acupuncture was related to the afferent nerve fiber in different layer with different intensities.