Inhibiting Effect Of The Diffuse Noxious Inhibitory Controls In Nociceptive Stimulus Induced By Electroacupuncture

PURPOSE: This study aims to explore whether the diffuse noxious inhibitory controls(DNIC)system has involved in the mechanism of analgesic effect by observing the difference of the systemic analgesic effect induced by electroacupuncture(EA)with different intensities.METHOD: Four experiments were conducted in animal and human body separately.The first one was animal behavioral experiment.In conscious rats,EA the ipsilateral and contralateral Zusanli point(ST36)with the intensity of 1m A(0.6Tc),3mA(Tc)and a frequency of 15 Hz.The changes of paw withdrawal mechanical threshold(PWMT)and it,s latency.The second one was C-fiber reflex experiment conducted on animals.Each SD male rat was anesthetized,the left sural nerve was stimulated by stimulation pulses delivered at a frequency of 0.2 Hz.Electro myographic reflex responses(EMGs)were recorded from the ipsilateral biceps femoris muscle.Then,the threshold of A? and C-fiber reflex were measured.After arised EMG response induced by the stimulation of 1.2Tc,EA stimuli were given on the skin overlying the ipsilateral and contralateral Zusanli point(ST36),and the strengths chosen were times of the threshold eliciting a nociceptive reflex response.The EMG response changes of frequency and amplitude induced by stimulating sural nerve at aintension of 1.2Tcwere observed after 0-5 min after EA to explore the analgesic effect of different intensity of EA.The third one was dQST experiment on human body in which ten eligible healthy volunteers are chosen asthe test subjects,4s47?thermal stimulation wasgiven to the left thenar eminence by a temperature sense analyzer,and then the subjects gave the visual analogue scale(VAS)values before,30 s,60s,90 s and 120 s after EA to analyze the changes of VAS values.The last one was R? reflex experiment on human body where a stimulus was given to the left sural nerve to get the R? reflex threshold values.After arised EMG response induced by the stimulation of 1.2Tr?,EA stimuli were given on the skin overlying the ipsilateral and contralateral Zusanli point(ST36),and the strengths chosen were times of the threshold eliciting a noticeptive relex response.The EMG response changes of frequency and amplitude induced by stimulate sural nerve at aintension of 1.2Tc were separately observed at 0-5 min after EA to explore the analgesic effect of different intensity of electroacupuncture.RESULT:(1)The result of the animal behavior experiment was basically consistent with that of the dQST experiment on human body.In the animal behavior experiment,the latency of paw withdrawal mechanical was 13.04±3.09(s)and the threshold value was 13.28±3.02(g).Both the threshold and latency of paw withdrawal mechanical were increased after EA with the two kinds of intensity.(p<0.05,n=10).In the dQST experiment on human body,the average value of the visual analogue scale(VAS)is 61.5±8.1.The VAS values of the subjects decrease and their pain tolerance values rise after EA(p<0.05,n=10).What's more,the greater the intensity of the EA was,the higher the pain threshold of rats and human bodies was.(2)The result of the C-fiber reflex experiment on animal was basically consistent with that of the R? reflex experiment on human body.It's shown from the C-fiber reflex experiment that the threshold of A?reflex(TA?)was0.54±0.23 mA,and the threshold of C-fiber reflex(TC)was 2.92±0.39 mA.EA of 1.2Tc reduced the frequency of EMG induced by C-fiber reflex with the intensity of Tc and 2Tc,while with the intensity of 0.8Ta,the inhibition effect was of C-fiber reflex was not obvious.The threshold of R? reflex in 10 human is 7.95±1.8mA.With the increase of the intensity of EA it,s inhibitory effect on the EMG would also improve.CONCLUSION: The inhibitory effect and time of the conditioned stimulus on the test stimulus strengthens with the increase of the intensity of EA.The conditioned stimulus is one of the key factors that decide the Acupuncture Analgesia.The intensity of EA induced by C-fiber reflex inhibited the contralateral EMG response,realizing the analgesic effect.The diffuse noxious inhibitory controls(DNIC)system has involved in the mechanism of analgesic effect applied at heterotopic acupoints,meanwhile other analgesic mechanism may also participate in.