The Effect Of Different Voltage Pulsed Radio Frequency On The Beta-endorphin In The Hypothalamus Of CCI Rat Model

Objective:To observe the effect of different voltage pulsed radiofrequency(PRF)on the content of beta-endorphin in the hypothalamus of CCI rat model,and explore the analgesic mechanism of pulsed radiofrequency.Methods:After seventy-two male SD rats received an operation of chronic constriction injury of sciatic nerve,they were all randomly divided into 4 groups(n=18): Sham operation group H0,PRF low voltage group H1(45V),PRF medium voltage group H2(55v),PRF high voltage group H3(65V).PRF groups: On the 7th of post-operation PRF needles was placed in the proximal sciatic nerve with pulse duration of 20 ms,pulse rate of 2Hz,treatment time of 2 min,and output voltage of 45 V,55v,65 v respectively;While in H0 group,PRF needles were placed in the same location for 2 min without radiofrequency stimulation.Pain behavioral changes were measured before operation(T0),7th postoperative day(T1)and 1(T2),7(T3),14(T4)days after PRF treatment.The expression of beta-endorphin were respectively measured in the hypothalamus in each group(n=6)at l,7,14 days after PRF treatment and observed the changes of microstructure under electron microscope.Result:At 1,7,14 days after PRF treatment,paw withdrawal thermal latency(PWTL)of PRF groups were all increased significantly comparing with sham operation group.On the 7thday after the operation,PWTL of the medium and high voltage group was significantly higher than the low voltage group(P < 0.01).At the end of the experiment,the expression of beta-endorphin in PRF groups were significantly higher than sham operation group(P < 0.01).On the 7th day and 14 th after the operation,the expression of beta-endorphin of the medium and high voltage group were increased significantly comparing with the low voltage group(P < 0.01).On the 14 th day after the operation,there were differences between medium and high voltage group(P < 0.05);Under the electron microscope,the sciatic nerve injury was slight by PRF stimulation compared with the sham operation group.Conclusion:1.PRF(frequency 2Hz)of the low,medium and high voltage group can all cause the increase of the PWTL of CCI rats,which may be related to the increase of the content of beta-endorphin in the hypothalamus.At the same time,the needle tip temperature fluctuation is small,and it is speculated that the field effect of different voltage may be one of the mechanisms of PRF analgesia.2.When the pulsed radiofrequency voltage is greater than 55 V,the pain threshold reduction did not further improve.However,beta-endorphin content has an upward trend,may prolong the time of pain relief.