Effects Of Psychological Stress On The Histology And Molecular Biology Of Masseter Muscle In Rats

Objective:More and more attention has been paid to the relationship between psychological stress and the occurrence and development of psychosomatic diseases.Oral normal occlusal function is chewing muscles,the temporomandibular joint,the relationship between the teeth in the central nervous system under the action of mutual support,mutual restriction,the result of the masseter as an important part of masticatory muscle,due to its location shallow,dominant nerve is rich,ontology sensory feedback effect is stronger,muscle fiber type complex reasons,such as more timely and sensitive response to external stimuli.In addition,the distribution density of proprioceptor such as muscle spindle in the ascending jaw muscle is higher than that in the descending jaw muscle,and the masseter muscle is a pair of muscles with the highest distribution density of muscle spindle in the ascending jaw muscle and the most timely and sensitive response to various stress states.Modern medicine has made some progress in the research on the effects of psychological stress on the oropharmaxillary muscles.Epidemiology has proved that the diseases of the oropharmaxillary system are closely related to psychological stress.However,the changes of the histology and related molecular biology of the masseter muscles after psychological stress are still unclear,and further research is needed.This experiment through the establishment of rats with chronic psychological stress model,from the general condition of rats,behavioral science,serological related evaluation index evaluation after the success of the three dimensions confirmed that the psychological stress rats,from changes in masseter histology,oxidative stress factor and decoupling even protein 2 expression changes and correlation analysis to explore the psychological stress influence on muscle histology and molecular biology,for more in-depth research to provide experimental basis for psychological stress result in masticatory muscle disorders.Methods:1.Establishment and evaluation of rat psychological stress model:Chronic bondage stress（chronic restraint stress,CRS）method to establish model of psychological stress rats randomly assigned into blank group,the psychological stress group,NC in bondage stress for 14 days,21 days,28 days,to evaluate the general physical condition of rats and measurement,at the same time use the behavior such as kuang field test evaluation methods and serological indexes adrenocorticotropic hormone（adrenocorticotropic hormone,ACTH）,corticosterone（corticosterone,CORT）,To evaluate the chronic binding stress model.2.Histological observation of the masseter muscle of rats after psychological stress:the tissue of the masseter muscle of rats in each group was collected,and the macroscopic and microscopic histological changes of the masseter muscle were observed under the microscope.3.Effects of psychological stress on oxidative stress indexes and DEC2 in rat masseter muscle tissue.After making masticatory muscle homogenate,the expressions of hydrogen peroxide,malondialdehyde,superoxide dismutase,8-hydroxy-deoxyguanosine and DEC2 in masseter muscle were detected by double-antibody sandwich ELISA.Results:（1）The masseter muscle of the rats removed after anatomy was covered with connective tissue,and the muscular part was composed of muscle fibers.The masseter muscle tissue of the experimental group and the control group were soft and red,and there was no significant difference between them.（2）In the NC group,muscle fibers were arranged neatly with uniform thickness.He staining in the CRS group showed that after 2weeks of modeling,the muscle fibers were arranged slightly disorderly,a small amount of inflammatory cell infiltration was observed in the muscle fibers,and the blood vessels were slightly dilated.After 3 weeks of modeling,the muscle fibers were slightly disordered,with increased infiltration of inflammatory cells between the muscle fibers and vasodilation.At 4 weeks of modeling,the masseterus tissue interstitium was hyperemic,with red blood cell exudation,blurred transverse striations,and muscle contraction bands were visible.（2）SOD activity showed that the CRS2 week group decreased compared with the NC group,and the difference was statistically significant（P<0.01）.SOD activity in CRS3week group was decreased compared with NC group,and the difference was statistically significant（P<0.05）.SOD activity in CRS4-week group was significantly lower than that in NC group,and the difference was statistically significant（P<0.01）.MDA results showed that compared with NC group,the content of MDA in the masseter muscle of CRS group was significantly increased.Compared with NC group,the content of weekly CRS2 group was increased to a certain extent,and the difference was statistically significant（P<0.01）.Compared with the NC group,the content of CRS3 week group was significantly increased,and the statistical significance was extremely significant（P<0.001）.Compared with NC group,the content of CRS in 4-week group was significantly increased,with statistical significance（P<0.01）.H₂O₂ results show that compared with NC group,CRS group were significantly higher in the rat masseter H₂O₂ content,CRS2weeks compared with NC group content has a certain set of rise but there was no statistically significant difference,CRS group 3 weeks and compared with NC group content has increased and the difference was statistically significant（P<0.05）,CRS4group increased significantly compared with NC group content,and a significant statistical significance（P<0.01）.The 8-OHDG results showed that compared with the NC group,the 8-OHDG content in the mass muscle of rats in the CRS group was significantly increased,and the 8-OHDG content in the CRS2 week group,the 3-week CRSgroup and the 4-week CRSgroup was significantly increased compared with the NC group,with statistical significance（P<0.001）.The content of 8-OHDG in CRS group decreased with time,but the difference was not statistically significant.UCP2 results showed that:compared with the NC group,the UCP2 content in the masseter muscle of rats in the CRS group was significantly increased,and the UCP2 content in the CRS2group,the CRS3-week group and the CRS4-week group was significantly increased compared with the NC group,with statistical significance（P<0.001）.The content of8-OHDG in CRS3-week group and CRS4-week group was significantly higher than that in CRS2 week group（P<0.01）.The CRS4-week group showed a downward trend compared with the CRS3-week group,but the difference was not statistically significant.The results showed that UCP2 was positively correlated with the contents of8-OHDG,H₂O₂ and MDA in masseter muscle（P<0.001）,and negatively correlated with SOD content（P<0.001）.Conclusion:Psychological stress can cause the injury of masseter muscle and oxidative stress in rats,and UCP2 overexpression is closely related to oxidative stress.