| Objective: Myofascial pain syndrome is a clinically prevalent injury and a common cause of soft tissue pain.IASTM have been shown to be effective in treating soft tissue injuries by reducing pain,removing scar adhesions,promoting regeneration of damaged tissues,and restoring limb function,but little research has been done on the mechanism of the therapeutic effects of IASTM.In this study,we investigated the mechanism of IASTM treatment for myofascial pain syndrome by observing the effects of central and peripheral substance P,5-hydroxytryptamine and bradykinin expression and histomorphological changes after IASTM intervention in myofascial pain trigger point model rats.Methods: Fifty-six healthy male 10-week-old SD rats were divided into three groups: 16 in the control group（CG）;40 in the modeling group were randomly selected 8 to test whether the modeling was successful after the completion of modeling,and the remaining 32 were divided into two groups,16 in the model group（MG）and 16 in the IASTM group（IG）.In this study,blunt strikes combined with centrifugal running were used for modeling,and the striking treatment was performed on Monday of the first eight weeks: a striking device with a weight of 1200 g was dropped from a height of 20 cm and struck the marked area of the medial femoral muscle,and each rat was struck once a week.Centrifugal running was performed on Tuesdays,with the requirement of timing for 90 min at a speed of 16 m/min and a running table angle of-16°.The IASTM intervention was started twice a week for four weeks after the end of the modeling and the pressure pain threshold was measured.At the end of the intervention,the rats were executed and the SP content of hypothalamus,serum and local tissues,5-hydroxytryptamine content of left and right brain,serum and local tissues,and bradykinin expression of local tissues were measured,and tissue sections were prepared.The obtained data were statistically analyzed by SPSS 26.0 using one-way ANOVA with P（27）0.05 as the level of significance of differences.Results: 1 、 Pressure Pain Threshold results: before modeling there was no significant difference between the three groups（P（29）0.05）;after the end of modeling the pressure pain threshold of rats in the MG and IG was significantly lower compared to the CG,and there was a significant difference（P（27）0.05）;after the end of intervention,the pressure pain threshold of both the MG and IG increased significantly,but the higher value in the IG was significantly greater than that in the MG.2 、 ELISA results: SP and 5-HT levels were significantly higher in the MG compared with the CG（P（27）0.05）.Compared with the MG,the 5-HT content in blood was significantly lower in the intervention group（P（27）0.05）,and the 5-HT content in local tissues at the trigger point tended to decrease,but there was no significant difference（P（29）0.05）,and the 5-HT content in the left and right brains was significantly higher,and there was a significant difference（P（27）0.05）;compared with the MG,the SP content in blood and local tissues of the trigger point was significantly lower in the IG（P（27）0.05）,and significantly higher in the hypothalamus（P（27）0.05）.3、Immunohistochemical results: The expression level of BK in the local tissues of trigger point of rats in the MG was significantly higher compared with that in the CG（P（27）0.05）;the expression level of BK in the local tissues of trigger point of rats in the IG was significantly lower compared with that in the MG（P（27）0.05）.4 、 HE staining light microscopic observation results: the morphology of myocytes in the CG was regular and the myofibers were arranged in an orderly manner;the myocytes in the MG showed edema and inflammatory infiltration,the thickness of myofibers was different and some of them were broken;most of the myocytes in the IG had been repaired and the inflammatory infiltration condition was improved,the myofibers still had some distortion but were arranged in a slightly regular manner.Conclusion: 1、After experimental study,it was found that IASTM intervention can effectively reduce the content of substance P,bradykinin and substance P and5-hydroxytryptamine in the local tissues at the trigger point,which is conducive to pain relief.2、After IASTM intervention,it was found that the content of substance P and 5-hydroxytryptamine in the center is increased,which can activate the downstream pain modulation system to relieve pain.3、IASTM can loosen the local tissue at the trigger point of myofascial pain adhesions,promote tissue repair,and facilitate the recovery of local damaged tissue myofiber morphology. |
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