Effects Of Pulsed Radiofrequency On Nerve Repair And Expressions Of GFAP And GDNF In Rats With Neuropathic Pain

Objective:Neuropathic pain(NP)is a common chronic pain in clinic.It is caused by the damage of somatosensory system or diseases,such as the damage of nervous system,ischemia,infection,metabolic diseases,nerve compression,etc.,which makes the pain threshold greatly reduced,and the expression of neuron excitability increased such as abnormal pain,spontaneous pain,hyperalgesia and sensory abnormality appears,which seriously affects the patient's performance Mood and quality of life.The pathogenesis of neuropathic pain is complex(mainly including functional damage and anatomical structure changes),including central sensitization,peripheral sensitization,activation of spinal glial cells,dysfunction of descending inhibition system,changes in ion channels and other mechanisms.The possible pathological changes include: neurogenic inflammation,nerve injury,sympathetic nervous system abnormality,peripheral nerve excitability abnormality and nerve plasticity change.Therefore,the clinical treatment of neuropathic pain is still lack of ideal methods,oral medicine,physical therapy and acupuncture and other traditional treatment methods have limited effect.Neuropathic pain is a continuous process,the condition may appear repeatedly,more than half of patients with neuropathic pain suffer from pain,and the pain can not be fully relieved.Pulse radio frequency(PRF)was first used in analgesia treatment by sluijter in 1997.It is achieved by the closed circuit formed with human body,the impulse radio frequency current released at the end of electrode,the pulse current formed near the target nerve tissue,interfering or blocking the conduction of pain signal,and inhibiting the nociceptive afferent of peripheral nerve C fiber.As a new pain treatment technology,it has become one of the important methods to study and treat pathological neuralgia in the future due to its advantages of convenient operation,high safety,small trauma,less complications and significant curative effect.At present,as a pain interventional therapy technology,pulse radio frequency is widely used in the clinical treatment of neuropathic pain,but its mechanism is not completely clear.Glial fibrillary acidic protein(GFAP)is a well-known astrocyte marker protein.GDNF plays an important role in regulating pain signal transduction,especially in the stage of neuropathic pain.It has been proved that radiofrequency pulse therapy can alleviate the disease in the ligation site of sciatic nerve in rats with chronic sciatic nerve constriction injury Based on rational neuralgia,this study explored the effect of impulse radiofrequency therapy on the repair of injured sciatic nerve by observing the changes of behavior and histology,and explored the changes of astrocyte quantity and morphology in the process of repairing the damaged nerve by measuring the expression of GFAP and GDNF in the nerve tissue of rats,and explored the changes of astrocyte quantity and morphology in the process of repairing the damaged nerve by impulse radiofrequency therapy The possible mechanism of source pain.Methods:90 clean and healthy adult male SD rats were selected and fed at 22-24 ° C,40-70% humidity and normal circadian rhythm.They were randomly divided into control group(C group),sham operation group(PS group)and partial sciatic nerve ligation(PSNL)+ pulse radio frequency(PRF)group(PR group).The mechanical pain threshold of PS group and PR group at 1,3,7 and 14 days after operation and the corresponding time point of the control group were measured with von Frey tactile pain detector.15 rats were randomly selected for observation each time.At the end of 1,3,7 and 14 days after PRF,5 rats in each group were killed.The remaining rats in PR group and PS group were all killed on the 14 th day after the treatment.The pathological sections of sciatic nerve were made,and the spinal cord tissues were weighed and prepared for use.The same treatment was performed in the control group at the same time.By observing the general behavior of rats in the course of treatment,and measuring its mechanical and thermal hyperalgesia.Enzyme linked immunosorbent assay(ELISA)was used to detect the content of inflammatory factors in spinal cord.Quantitative reverse transcription polymerase chain reaction(QRT PCR)and Western blotting were used to detect the changes of GFAP and GDNF gene and protein levels in nerve tissues.Results:1.Rats in group C were free to move,regular to drink water,normal to move and good to environment.In PS group,there were different degrees of claudication,weakness of lower limbs,toe folding and valgus,nerve injury and other behavioral changes.After PRF,the symptoms gradually decreased with the prolongation of the treatment time,which was close to group C at 14 days.2.The MWT of PS group was significantly lower than that of C group(P < 0.05),PR group was significantly higher than that of PS group(P < 0.05),which was similar to that of C group.3.The TWL of the PS group was significantly shorter than that of the C group(P < 0.05)on the 1st,3rd,7th and 14 th day after operation,and that of the PR group was significantly longer than that of the PS group(P < 0.05).4.The levels of IL-1 and TNF-? increased in PS group at 1,3,7 and 14 days after operation(P < 0.05),and decreased in PR group(P < 0.05).5.HE staining showed that the sciatic nerve of group C had no pathological changes,normal structure and orderly arrangement of nerve cells.In PS group,the nerve fibers were disordered.In PR group,nerve fibers gathered in sciatic nerve tissue and began to rearrange.6.The mRNA expression level of GFAP in PS group was increased at 1,3,7 and 14 days after operation(P < 0.05),but decreased in PR group compared with PS group(P < 0.05).At the same time,the mRNA expression level of GDNF showed the opposite trend.7.The protein expression level of GFAP in PS group increased 14 days after operation(P < 0.05).Compared with PS group,the protein expression level of GFAP in PR group decreased(P < 0.05).But the protein expression of GDNF showed the opposite trend.Conclusion:Nerve injury can cause a series of pathological changes such as inflammatory reaction and nerve dysfunction,which can lead to neuropathic pain.PRF may significantly inhibit the expression of GFAP by activating the expression of GDNF,so as to reduce the occurrence of neuropathic pain,and at the same time,it may play a role in repairing the nerves injured by neuropathic pain.