Swimming Mediates Pain Hypesensitivity In A Lumbar Disc Herniation Rat Model

Background:Neuropathic pain,which is the major symptom of lumbar disc herniation(LDH),causes a heavy burden on society.However,the pain mechanism in lumbar disc herniation has not been fully understood yet.Therefore,seeking for a suitable way to mediate such chronic neuropathic pain can bring LDH patients a better rehabilitation guidance.Swimming,as a convenient exercise manner,can efficiently strengthen back muscles without too much load.Comparing with other exercise manners(such as Treadmill,Yoga),it can extremely decrease the danger factor that aggravates low back pain which mainly caused by excessive exercise.In our research,we establish the lumbar disc herniation model in rats:200g to 220g SD male rats,the left nerve roots of rats’ lumbar 5 and 6 are exposed after anesthesia,and the normal nucleus pulposus tissue of the proximal caudal vertebra of rats are taken and placed on its surface.Besides,we establish swimming model:after three days of adaptation,rats are given adaptive swimming exercise:10 minutes each day for two days.Then,these rats suffer a LDH modeling surgery.4 days later,10 minutes of swimming exercise would be carried out,10 minutes of exercise time would be added to 30 minutes each day,and then 30 minutes of swimming exercise will be maintained from the seventh day after surgery to the twenty-eighth day after surgery.During this period,the mechanical pain and thermal pain threshold of rats are detected by von frey instrument and hot tingling apparatus.we also use western blotting to analyse the differential expression of NF-kb,P2X family and Toll-like receptor family in the swimming group and LDH group.Our research will explore whether swimming can mediate neuropathic pain and the exact meditating mechanism.The results:Compared LDH group with sham group,it shows a lower mechanical pain threshold and thermal pain threshold especially at day 7 after surgery.But when we compared swimming group with LDH group,It has a higher pain threshold from day 7 to day 21 after surgery,especially in day 14.So,we sacrificed rats at day 14 after surgery,western blotting indicates that there is a lower expression of NF-kb,P2X7 receptor,Toll-like receptor4 in swimming group compared with LDH group,and there is a higher expression of P2X4 receptor in swimming group compared with LDH group while the expressions of oxytocin receptor,P2X1 receptor,P2X2 receptor,Toll-like receptor 7 has no significant difference compared with LDH group.Conclusion:Our findings reveal that swimming can mediate persistent pain hypersensitivity in the rat model of LDH.NF-kb,Toll-like 4 receptor,P2X4 receptor,P2X7 receptor may participate in the process of analgesia.Further research is needed to explore the exact mechanism.