OBJECTIVETo observe the intervention effect of electroacupuncture (EA) at "Weizhong" (BL 40) on rats with bupivacaine-induced multifidus muscle injury, so as to explore the action mechanism.

METHODSA total of 72 rats were randomly divided into a control group, a model group, a Weizhong group and a Shenshu group, 18 rats in each group. Each group was again randomly divided into a 4-day subgroup, a 7-day subgroup and a 14-day subgroup, 6 rats in each subgroup. Rats in the model group, Weizhong group and Shenshu group were treated with intramuscular injection of 0.5% bupivacaine (BPVC) to establish the model of multifidus muscle injury. Rats in the Weizhong group and Shenshu group were treated with EA at "Weizhong" (BL 40) and "Shenshu" (BL 23), 20 min per treatment, once a day. Each subgroup was treated for 4 days, 7 days and 14 days respectively. Rats in the control group and model group were treated with immobilization. The morphology and cross sectional area (CSA) changes of multifidus with HE and Masson staining at different time points were observed; the expression of insulin like growth factor 1 (IGF-1) and myogenic differentiation antigen (MyoD) was measured by immunohistochemical method.

RESULTSAfter the modeling, there were significant morphology changes of multifidus at different time points, which was not fully recovered after 14 days. The morphological observation in the Weizhong group and Shenshu group was superior to that in the model group. At 7th day, the CSA in the Weizhong group was higher than that in the model group (P < 0.05); at 14th day, the CSA in the Weizhong group and Shenshu group was higher than that in the model group (P < 0.01, P < 0.05). At 4th day and 7th day, the expression of IGF-1 in the model group was higher than that in the control group (both P < 0.01); at 4th day, that in the Weizhong group was higher than that in the model group (P < 0.01), and that in the Weizhong group was higher than that in the Shenshu group (P < 0.05), and that in the Shenshu group was as higher than that in the model group (P < 0.05); at 14th day, that in the Shenshu group was higher than that in the model and Weizhong group (P < 0.01). At 4th day, the expression of MyoD in the Weizhong group and Shenshu group was higher than that in the model group (P < 0.01), which was more significant in the Weizhong group (P < 0.01).

CONCLUSIONElectroacupuncture at "Weizhong" (BL 40) and "Shenshu" (BL 23) can both promote the regeneration of multifidus muscle injury. EA at "Weizhong" (BL 40) has a better effect at early phase, which may be related to the up-regulation of IGF-1 and MyoD and the completion of the proliferation of myoblast in advance.