Advantage Pulse Width Study Of Different Frequency Electro-acupuncture Intervention Of Inflammatory Pain In Rats

Objective Using the electrical stimulation on healthy SD(Sprague-Dawley)male rats to conduct the preliminary screening of the optimization parameter frequency and wave wide.Observing the pain threshold of the inflammatory model rats,and detecting the paw tissue Interleukin-1β(IL-1β),Tumor Necrosis Factor-a(TNF-α)and the central thalamus Leucine-enkephalin(L-ENK)and β-endorphin(β-END)concentration,verify and evaluate the combinations of parameters of electrical stimulation analgesia effect to filter out the best combination of parameters in treatment of inflammatory pain.Methods First part:210 healthy SD male rats,were assigned in a random manner to one of the three groups(2Hz,100Hz,120Hz).Each group including seven pulse width(50μs,100μs,200ps,300μs,400μs,500μs,600μs),which contained 10 rats.Using electrical pulse stimulator to intervene the healthy rats on the right Zusanli(ST36)and Kunlun(BL60),1mA for 15min,2mA for 15min,totally 30 minutes for only one time.Then,Withdrawl Thresholds were measured before the stimulation(Base)and after(After),respectively by using Digital Von Frey(EVF)pain measurement instrument.Second part:30 healthy SD male rats were randomly divided into Normal group(N group),Model group(M group),Electrical stimulation group(EA group).Establish the rat model of inflammatory pain by injecting CFA to SD rats’ right plantar surface.EA group was started on day 1 after CFA operation and then given the electrical stimulation on ipsilateral of Zusanli(ST36)and Kunlun(BL60)daily for 10 days with the pulse electrical stimulator,1mA for 15min,2mA for 15min,for a total of 30 minutes.Then the EA group was divided into three subgroups(continuous wave 100Hz/200μs;120Hz/300ps;2(50μs)/120Hz),according to different combinations of frequencies and wave wide.The Withdrawl Thresholds of each rat were measured as an assessment of nociception before and 24 hours after operation and day 1,3,5,7,10 after the treatment,which were measured respectively by using EVF;The hypothalamic β-END and L-ENK concentration was measured by Radioimmunoassay(RIA);And the right rat paw tissue IL-1β and TNF-αconcentration was measured by Enzyme-linked immunosorbent assay(ELISA).Results The immediate analgesic effect of 2Hz(50μs)with low frequency stimulation on normal rats was superior to other wave width(P<0.01);the immediate analgesic effect of 100Hz(200μs)with high frequency stimulation on normal rats was the best(P<0.01);the immediate analgesic effect of 120Hz/300μs on healthy rats was the best(P<0.01);compared with the N group,the PWTs of rats in each group were significantly decreased after modeling(P<0.01);compared with the M group,the PWTs of rats in each EA group after electrical stimulation intervention was significantly increased(P<0.01);compared with the EA group,the PWTs of rats in 2/120Hz group after one week intervention changed obviously(P<0.01);compared with the M group,the concentration of L-ENK in hypothalamus of each EA group were significantly increased(P<0.01),compared with EA group,the effect of 2/120Hz was the best(P<0.05);compared with the M group,the concentration of β-END in the hypothalamus of each EA group was significantly increased(P<0.05),the effect of 2/120Hz was better than other EA groups;compared with the N group,the concentration of IL-1 and TNF-α in M group were significantly increased(P<0.01),the concentration of IL-1β and TNF-α were reduced after electrical pulse stimulation interventions,compared with the M group,the concentration of TNF-α in each EA group was significantly lower(P<0.01).Conclusion Different frequencies and wave wide parameter combinations can have some impact on pain threshold of healthy rats.Electrical stimulation intervention on CFA-induced inflammatory pain rats has satisfactory analgesic effect,and different frequency and pulse width of electrical stimulation[100Hz/200μs;120Hz/300μs and 2(50μs)/120Hz]may has optimal combination of parameters,probably by regulating the CFA model of central opioid peptides and peripheral inflammatory factors,which plays an role in anti-inflammatory analgesic effect.Among them,the effect of parameters combination on 2/120Hz is optimal.