Effects of silver needle diathermy on myofascial pain syndrome and the expression of SP, NGF, IL-1β, TNF-α in rats

Objective To observe the effects of silver needle diathermy on myofascial pain syndrome (MPS) and the expression of substance P, nerve growth factor, interleukin-1 beta, tumor necrosis factor-alpha in rats. Methods Twenty-four Sprague-Dawley rats were randomly divided into three groups: control, MPS model and treatment groups. The rats in the model and treatment groups were copied the MPS model by traumas on right femoral muscle combined with eccentric exercise, and the treatment group were received thermal acupuncture with silver needle. The change of gait, electro-myography, thermal hyperalgesia, concentration of SP, NGF, IL-1β, TNF-α in local muscle and serum, and local muscle tissue biopsy were observed and compared between the three groups in all rats. Results (1) Gait: No limp occurred in right hindlimb in the control group at the time of MPS model completed (T1) , but the incidence of limp was 100% in the model and treatment groups. The incidence of limp was 100% (8/8 rats) in the model group and 12.5% (1/8 rats) in the treatment group at the 3rd week after the silver needle diathermy (T2) . (2) EMG: No spontaneous electrical activity (SEA) occurred in right femoral muscle at T1 in the control group, but appeared in the model and treatment groups. The frequency of SEA was significantly lower in the treatment group than that in the model group at T2 (P<0.01) . (3) Thermal hyperalgesia: The thermal withdrawal latency (TWL) was reduced in the model and treatment groups as compared with the control group at T1 (P<0.01) . The TWL was longer in the treatment group as compared with model group at T2 (P<0.01) . (4) The expression of SP, NGF, IL-1β and TNF-α in local muscle tissue was significantly higher in the model group as compared with the control group at T2 (P<0.01) , and decreased in the treatment group as compared with the model group (P<0.01) . (5) The expression of SP, NGF, IL-1β and TNF-α in serum was significantly higher in the model group as compared with the control group at T2 (P<0.01) , and decreased in the treatment group as compared with the model group (P<0.01) . (6) Muscle biopsy by HE stained at T2: The control group showed normal configuration, while obviously disorder nodules and muscle fiber structure, thickened sarcolemma in the model group, and new capillaries appeared in the treatment group. Conclusion Silver needle diathermy is an effective method in the treatment of rats with MPS by down-regulation of the expression of SP, NGF, IL-1β and TNF-α in local muscle tissue. Key words: Myofascial pain syndrome; Silver needle; Substance P; Nerve growth factor; Interleukin-1 beta; Tumor necrosis factor-alpha