The Effects Of Pulsed Radio Frequency At Different Time On The Beta-endorphin In The Hypothalamus Of CCI Rat Model

Objective:To observe the effects of pulsed radiofrequency with different treatment times on the beta-endorphin in hypothalamus in a rat model of chronic neuropathnic pain.Method:Seventy-two male SD rats weighing 200-220 g were randomly divided into 4groups(n=18 in each group):Sham PRF group(A0),PRF 120 s group(A1),PRF 480 s group(A2),PRF 720 s group(A3).Neuropathnic pain was induced by chronic constrictive injury(CCI).PRF intervention was performed on the proximal part of the sciatic nerve ligation in group PRF at 7 d after CCI,with pulse duration of 20 ms,pulse frequency 2Hz,voltage 55 v,and the duration of treatment time was 120 s,480s,720 s respectively.The radiofrequency electrodes were placed at the same position of sciatic nerve without electricity applied in sham PRF group.Pain behavioral changes were measured before operation(T0),7th postoperative day(T1)and 1(T2),7(T3),14(T4)day after PRF treatment.The expression of beta-endorphin by enzyme-linked immunosorbent assay(ELISA)were respectively measured in the hypothalamus in each group(n=6)at 7?14?21 days after PRF treatment and the histological changes of the sciatic nerve in rats were observed under light microscope.Result:At 7,14,21 days after PRF treatment,PWTL of PRF groups were all increased significsntly comparing with sham operation group.PTWL of PRF 120 s group was significantly lower than PRF 720 s group and PRF 480 s group at 21 d after PRF treament(P<0.05),which was higher in PRF 720 s group than that in PRF 480 s group(P<0.05).The expression of beta-endorphin in the hypothalamus of the rats was significantly higher in the PRF group than in sham PRF group(P <0.01)at 7,14 d after PRF treatment.The expression of beta-endorphin was significantly higher in PRF 720 s group and PRF 480 s group than in PRF 120 s group at 14 d after PRF treament(P<0.05),which was higher in PRF 720 s group than that in PRF 480 s group(P <0.05),higher in PRF 480 s group than that in PRF 120 s group at 21 d after PRF treatment(P<0.05).The sciatic nerve structure changeds lightly after PRF treatment,and showed a trend of recovery over time under light microscope.Conclusion:The PWTL of CCI rats is significantly increased after PRF treatment with120 s,480s and 720 s,which may be related to the increase of the content of beta-endorphin in hypothalamic.Appropriately increaseing the time of pulsed radiofrequency will maintain high concentration of beta-endorphin in the hypothalamus of CCI rats for a long time,and may prolong the time of PRF analgesia.