| Objective Selecting the superior parameters by observing different combinations of frequency and the width of the effect of electroacupuncture(EA)on pain threshold in normal rats.The inflammatory pain model was established,observing the analgesic effect of superior parameters of EA on inflammatory pain in rats,and influence of which on interleukin-1β(IL-β)and tumor necrosis factor-α(TNF-α)levels in foot pads tissue,β-endorphin(β-EP)levels in hypothalamus tissues,so as to screen the superior parameters of EA intervening on inflammatory pain.Methods Experiment 1:140 healthy male Sprague Dawley(SD)rats were divided into two large groups in accordance with the frequency of 2Hz and 100Hz,each large group 70 rats,each large group was randomly divided into 7 groups in accordance with the wave width(50μs,100μs,200μs,300μs,400μs,500μs,600μs),each group 10 rats."Zusanli"(ST36)and "Kunlun"(BL60)acupoint of rats were selected to be applied electric stimulation and EA intensity was 1mA and 2mA every 15 min in succession for 1 time,and then mechanical paw withdrawal thresholds(PWTs)of rats were measured before and after acupuncture intervention.Experiment 2:30 healthy male SD rats were randomly divided into normal group(N),model(CFA)group,EA group 1(CFA+2Hz/50μs),EA group 2(CFA+2Hz/600μs),EA group 3(CFA+2/100Hz,2Hz,wave width for 50μs;100Hz,wave width for 200μs),Each group 6 rats.To establish the model of inflammatory pain,rats in group CFA and three EA groups were injected with CFA(0.1ml/only)under the right hind paw skin.Rats in group N were injected with equal amount of saline at the same position.1 day post CFA injection,the EA groups rats began to accept acupuncture intervention,selected ST36 and BL60 points of ipsilateral hind paw,stimulation parameters respectively were:2Hz/50μs;2Hz/600μs;2/100Hz(50μs/600μs).The intensity and time of EA were as same as Experiment 1,once a day,rats were continuously treated for 10 days.The remaining two groups were dealt with the same cloth cover without other treatment.The changes of PWL and PWTs were detected at time points of pre-CFA injection,24h post-CFA injection,and the 1st,3rd,5th,7th,9th,10th day after electroacupuncture intervention;the rats were killed and ipsilateral cushion tissues were taken on 10th day after EA intervention is ended,the levels of IL-1β and TNF-α in rat’s ipsilateral foot pad were detected by Enzyme linked immunosorbent assay(ELISA);the levels of β-EP in the hypothalamus were detected by radioimmunoassay(RIA).Results(1)The pain threshold of rats in the EA(2Hz/50μs)group is better than other wave width groups of same frequency at varying degrees,the pain threshold of rats in the EA(100Hz/200μs)group is better than other wave width groups of same frequency at varying degrees.(2)After CFA injection,the T-PWL and PWTs of each group rats were significantly decreased(P<0.01);compared with the CFA group,the T-PWL and PWTs of each EA group were both significantly prolonged and increased(P<0.05,P<0.01).The changes of T-PWL and PWTs were the most obvious in EA 3 group rats(P<0.05).(3)Compared with the rats in N group,the levels of IL-1β in rats’ footpad tissue of CFA group was significantly increased(P<0.01);compared with the CFA group,the levels of IL-1β was significantly decreased in all EA groups(P<0.01),there were no significant differences among the EA groups(P>0.05).(4)Compared with the rats in N group,the levels of TNF-α in rats’ foot pad tissue of CFA and all EA groups were both significantly increased(P<0.05);compared with the CFA group rats,the levels of TNF-α in rats’ foot pad tissue of EA 1 and 2 group have no significantly difference(P>0.05),the levels of TNF-α in rats’ foot pad tissue of EA 3 group was significantly decreased.(P<0.05).(5)Compared with the rats in N group,the levels of β-EP in rats’ hypothalamus of CFA group have no obvious difference;compared with the CFA group,the levels of β-EP in hypothalamus of all EA groups were significantly increased(P<0.05).There was no significant difference in the level of β-EP in the hypothalamus in the rats of each EA group.Conclusions EA has preferable effects on rats with inflammatory pain.Different frequencies,wave widths of EA have different anti-inflammatory and analgesic effects,which is probably related to regulation effects of EA on the levels of central opioid peptides and peripheral inflammatory factors. |
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