| Objective:Chronic pain is a common clinical symptom,but also a disease.Pain includes two components: pain sensation and pain emotion.The former reflects the property,intensity and position of the pain.The latter is induced by pain,which includes anxiety,disgust,fear and other negative emotions.With the deepening of people’s understanding,it is found that the pain emotion of chronic pain is often more serious than the pain itself.Therefore,the research on pain emotion is increasingly concerned.The related research from human and animal behavior,electrophysiology and brain imaging showed that the medial frontal lobe anterior cingulate cortex(anterior cingulate,cortex,r ACC)as an important nucleus of emotion circuit,the rostral part(rostral ACC,r ACC)plays a very important role in the process of pain emotion.It is well known that electroacupuncture activates opioid receptors to relieve pain,but does it also relieve pain emotion?Our previous studies and relevant laboratory data have demonstrated that electroacupuncture can also ease the pain emotion,Otherwise it has a significant alleviated effect on conditioned place preference induced by CFA(conditioned place avoidance,CPA)thro μ gh the activating opioid receptor and inhibiting NMDA receptor.There are many subtypes of opioid receptors,among which the most important are the three subtypes: Mu,Delta and kappa.As mentioned previously,we have demonstrated that the Mu opioid receptor is involved in mediating the effects of electroacupuncture on pain relief,but it is not clear whether the other receptor subtypes play a similar role.Therefore,this study will use the Delta opioid receptor as the research object,using the rat paw injecting CFA-induced conditioned place avoidance(C-CPA)for pain reaction model of emotional behavior,the behavior detection and multiple channel electrophysiological recording technique combining means to explore whether Delta opioid receptors are involved in alleviating pain and emotional effect of electroacupuncture.Methods:A home-made multichannel electrode with tube and tube.through the operation the multi-channel electrode with tube and tube were embedded r ACC,after SD rats recovered completely rats left foot were injected complete Freund’s adjuvant(CFA),induced inflammatory pain to establish conditioned place avoidance model,using micro injection pump,PE tube for injection of drugs,Pain feeling of behavioral changes was measured by rat foot withdrawal latency(PWL),the change of pain emotional behavior was measured by conditioned place avoidance device(CPA),at the same time using in vivo multi-channel and in vivo recording technology to record,process and analysis signal changes of r ACC neurons.The use of two factor grouping,specific patterns were as follows: 12 animal groups =2(CFA,saline)x 6(delta agonist: 5 dose,saline);8 animal groups(n=6-8 / group)=2(CFA,saline)* 2(delta antagonist,saline)* 2(EA,sham EA).Results:Behavior responses: rats foot after injection of CFA produce inflammatory pain,inducing condition location preference(CPA)model was set up;The r ACC area give different concentration of the delta opioid agonist DADLE to nociceptive stimuli of different impact conditions location preference(CPA),and low concentration DADLE had no obvious effect,with the increasing of the concentration,the inhibition had no obvious corresponding enhancement;Low doses of the delta-opioid agonist itself did not cause conditional reward.(1)Conditioned place avoidance(CPA)model1)Behavioral observation of conditioned place avoidance(CPA)model CFA+NS group and NS+NS group,before and after "pain environment" matching,thermal paw withdrawal latency of CFA+NS group had significant difference(P<0.05),before and after the "pain environment" matching,NS+NS group had no difference(P>0.05).The left side of the hind paw of the rats was injected with CFA,and the retraction latency(PWL)was significantly shortened,resulting in inflammatory pain.There was no difference in the "pain side" between the NS+NS group before and after the "pain environment"(P > 0.05).There was a difference in the "pain side" between the CFA+NS group before and after the "pain environment" matching(P < 0.05).CFA+NS group and NS+NS group avoidance score comparison had significant difference(P < 0.05).Before and after "pain environment" matching residence time in pain side shorten,and in the " non painful side " residence time was prolonged,obviously avoid the " pain environment ",establish CFA induced conditioned place avoidance model(CPA);2)Action potential of electrophysiological observation of conditioned place avoidance(CPA)model There was no difference in the discharge frequency of "pain side" and "non pain side" neurons in NS+NS group,(P > 0.05).There was a difference in the discharge frequency of "pain side" and "non pain side" neurons in CFA+NS group,(P < 0.05).CFA+NS group and NS+NS group after the "pain environment" matching in the pain side of the neuron discharge frequency comparison,had a difference(P < 0.05).3)Field potential of electrophysiological observation of conditioned place avoidance(CPA)model There was no difference in the frequency spectrum value of the five kinds of wave(Delta,theta,alpha,beta and lambda)of "pain side" and "non pain side" after the match of "pain environment" in NS+NS group(P > 0.05).The CFA+NS group "pain environment" matching "pain side" and "non painful side" Delta,theta,alpha,beta,lambda five wave frequency spectrum density values were different,(P< 0.05).CFA+NS group and NS+NS group,after the "pain environment" matching in "painful side" Delta,theta,alpha,beta,lambda five wave frequency corresponding to the frequency spectrum density values were different,(P< 0.05).In CFA rats,the action potential frequency and field potential amplitude of r ACC neurons were stronger than that of the control group in the pain environment than in the control group;(2)the activation of delta opioid receptor in relieving pain in rats1)Behavioral observation of the activation of delta opioid receptor in relieving pain in rats CFA+DADLE(0.625 / 1.25 / 2.5 / 5 / 10 μg/ul)group and CFA+NS group,before and after the "pain environment" in "painful side" retention time comparison,CFA+DADLE(1.25 /2.5 / 5 / 10 μg/ul)group,there was no significant difference(P >0.05);CFA+DADLE(0.625 μ g/ul)group and CFA+NS group,had significant difference(P < 0.05).CFA+DADLE(0.625 / 1.25 / 2.5 / 5 / 10 μ g/ul)group and CFA+NS group avoidance score comparison,CFA+DADLE(0.625 μg/ul)group and CFA+NS group had no significant difference(P > 0.05);CFA+DADLE(1.25 / 2.5 / 5 /10 μg/ul)group and CFA+NS group had significant difference(P < 0.05).The position of the r ACC region with different concentration conditions of delta opioid receptor agonist DADLE on CFA induced withdrawal(CPA)had different effects,too low concentration of DADLE had no obvious effect on CPA,with the increase of DADLE concentration,inhibition of CPA,but not increase inhibited effect with the increase of DADLE concentration increased;delta low dose of the opioid receptor agonist itself did not cause the conditioned reward.2)Action potential of electrophysiological effects of activated delta opioid receptors in relieving pain in rats There was no difference in the frequency of "pain side" and "pain side" neurons in CFA+DADLE group,(P > 0.05).CFA+DADLE group and CFA+NS group after the "pain environment" matching in the pain side of the neuron discharge frequency comparison,had a difference(P < 0.05).There was no difference in the frequency of "non pain side" and "pain side" neurons in NS+DADLE group,(P > 0.05).There was no difference between the NS+DADLE group and the NS+NS group after "pain environment" matching the "pain side" neuron discharge frequency,(P > 0.05).3)Field potential of electrophysiological effects of activated delta opioid receptors in relieving pain in rats There was no difference in the frequency spectrum value of the five kinds of wave of "pain side" and "non pain side" Delta,theta,alpha,beta and lambda after the match of "pain environment" in CFA+DADLE group(P > 0.05).There was no difference in the frequency spectrum value of the five kinds of wave of "pain side" and "non pain side" Delta,theta,alpha,beta and lambda after the match of "pain environment" in NS+DADLE group(P > 0.05).CFA+DADLE group and CFA+NS group,after the "pain environment" matching in "painful side" Delta,theta,alpha,beta,lambda five wave frequency corresponding to the frequency spectrum density values were different,(P<0.05).A certain concentration of delta opioid receptor agonist(DADLE)could reverse CFA induced electrical activity;(3)Electrophysiological study of the effects of delta opioid receptor mediated electroacupuncture on pain in rats1)The r ACC region was given different concentrations of delta opioid receptor antagonist,and rat was given electroacupuncture at the same time,it had no effect on CFA induced conditioned place avoidance(CPA).The other students in our experimental group had completed.2)Action potential of electrophysiological study of the effects of delta opioid receptor mediated electroacupuncture on pain in rats There was no difference in the frequency of "pain side" and "non pain side" neurons in NS+NS+sham EA group,(P > 0.05).There was a difference in the discharge frequency of "pain side" and "non pain side" neurons in CFA+NS+sham EA group,(P < 0.05).There was no difference in the frequency of "pain side" and "pain free" neurons in CFA+NS+EA group,(P > 0.05).There was a difference in the discharge frequency of "pain side" and "non pain side" neurons in CFA+Naltrindole+EA group,(P < 0.05).There was no difference in the frequency of "pain side" and "non pain side" neurons in NS+Naltrindole+sham EA group,(P > 0.05).CFA+NS+EA group and CFA+NS+sham EA group after the "pain environment" matching in the pain side of the neuron discharge frequency comparison,had a difference(P < 0.05).CFA+Naltrindole+EA group and CFA+NS+EA group after the "pain environment" matching in the pain side of the neuron discharge frequency comparison,had a difference(P < 0.05).There was no difference between the NS+Naltrindole+sham EA group and the NS+NS+sham EA group after the "pain environment" matching "pain side" neuron discharge frequency,(P > 0.05).3)Field potential electrophysiological study of the effects of delta opioid receptor mediated electroacupuncture on pain in rats There was no difference in the frequency spectrum value of the five kinds of wave of "pain side" and "non pain side" Delta,theta,alpha,beta and lambda after the match of "pain environment" in NS+NS+sham EA group(P > 0.05).The CFA+NS+sham EA group after "pain environment" matching "pain side" and "non painful side" Delta,theta,alpha,beta,lambda five wave frequency spectrum density values were different,(P< 0.05).There was no difference in the frequency spectrum value of the five kinds of wave of "pain side" and "non pain side" Delta,theta,alpha,beta and lambda after the match of "pain environment" in CFA+NS+EA group(P > 0.05).The CFA+Naltrindole+EA group after "pain environment" matching "pain side" and "non painful side" Delta,theta,alpha,beta,lambda five wave frequency spectrum density values were different,(P< 0.05).There was no difference in the frequency spectrum value of the five kinds of wave of "pain side" and "non pain side" Delta,theta,alpha,beta and lambda after the match of "pain environment" in NS+Naltrindole+sham EA group(P > 0.05).CFA+NS+sham EA group and CFA+NS+EA group,after the "pain environment" matching in "painful side" Delta,theta,alpha,beta,lambda five wave frequency corresponding to the frequency spectrum density values were different,(P < 0.05).CFA+NS+EA group and CFA+Naltrindole+EA group,after the "pain environment" matching in "painful side" Delta,theta,alpha,beta,lambda five wave frequency corresponding to the frequency spectrum density values were different,(P< 0.05).There was no difference between the NS+NS+sham EA group and the NS+Naltrindole+sham EA group after the "pain environment" matching in the "pain side" Delta,theta,alpha,beta,lambda five frequency wave corresponding to the frequency spectrum density value(P > 0.05).Electroacupuncture could attenuate CFA induced conditioned place avoidance response(CPA),and a certain concentration of delta opioid receptor antagonist(Naltrindole)could antagonize the effect of electroacupuncture.Conclusions:Throμgh this study we know that: 1)microinjection of opioid receptor agonist DADLE in ACC,activated partial opioid receptor,the rat paw injecting CFA-induced conditioned place avoidance(C-CPA)and reversal electrical activity produced by CFA;2)Electroacupuncture inhibit CPA reaction and electrical activity induced by CFA,which have been weakened by microinjecting opioid receptor antagonist in ACC,3)electroacupuncture can activate brain opioid receptor in r ACC of rat,weaken the conditioned place preference induced by CFA(CPA)reaction,and reverse the electrical activity induced by CFA. |
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