Effect of moxibustion on the expression of microglia and brain-derived neurotrophic factor protein in the spinal cord of rats with myofascial pain syndrome

Abstract

To observe the effect of moxibustion at myofascial trigger points on microglia activation and the expression of brain-derived neurotrophic factor (BDNF) in the spinal cord of rats with myofascial pain syndrome (MPS), so as to explore the central mechanism of the analgesic effect of moxibustion. Twenty-four male SD rats were randomly divi-ded into control, model and moxibustion groups (n=8 in each group). The MPS model was established by strinking on fascia musculares and eccentric exercise. Rats in the moxibustion group were treated with mild moxibustion at myofascial trigger point for 15 min, once daily for 7 days. The thermal withdrawal latency (TWL) of rats was measured with a hot stabbing instrument. The pathological changes of the rat medial femoris muscle were observed after H.E. staining. The expressions of microglia marker (OX-42) and BDNF in the spinal dorsal horn were detected by immunohistochemistry and Western blot, separately. After modeling, the TWL of both the model and the moxibustion groups were significantly down-regulated (P<0.01)，and were significantly decreased in contrast to that of the control group (P<0.01). After treatment and compared with the model group, the TWL of the moxibustion group was significantly increased (P<0.01) in the moxibustion group. Rat's muscle fibers of the control group were uniform in thickness and arranged tightly and regularly. While in the model group, some fractures and connective structure tissue renewal, irregular arrangement, and inflammatory cell infiltration were seen. The morphology of muscle fibers in the moxibustion group was close to normal, and the arrangement was neat and orderly, with a small amount of inflammatory cell infiltration. Compared with the control group, the expression of OX-42 and BDNF in the spinal dorsal horn of rats in the model group was increased(P<0.01). Following the treatment, and in comparison with the model group, the expression of OX-42 and BDNF of moxibustion group was down-regulated(P<0.05). Moxibustion can significantly improve the injury of the medial femoral muscle and the TWL in MPS rats，which may be related to its effects in inhibiting the activation of spinal dorsal horn microglia and reducing the expression of BDNF.