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《Acupuncture Research》 2007-05
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Observation on the Analgesic Effect of Repeated Electroacupuncture and Its Relation to Changes of Plasma β-EP,ACTH and COR Levels

LIU Jun-ling,CHEN Shu-ping,GAO Yong-hui,MENG Fan-ying,WANG Jun-ying(Institute of Acu-moxibustion,China Academy of Chinese Medical Sciences,Beijing 100700,China)  
Objective: To observe the regularity of electroacupuncture(EA) analgesia and to analyze its relation to hypothalamus-pituitary-adrenal cortex axis function in chronic constrictive injury(CCI) and ovariectomy(OVX) rats.Methods: A total of 110 Wistar rats anesthetized with mixture solution of 1.5% chloralose(50 mg/kg) and 25% urethrane(420 mg/kg,i.p.) were randomized into control(n=10),CCI(n=10),CCI+EA(n=30),OVX+CCI(n=30),OVX+CCI+EA(n=30) groups,and the later 3 groups were further divided into 2 times(2 t),2 weeks(2 w)and 3 w time courses,with 10 cases in each.Forty-five days after OVX,Morris water maze test was conducted to evaluate the OVX rats' memory-learning ability.Chronic pain model was established by ligating the right sciatic nerve with a piece of suture.EA(2/15 Hz,1 mA) was applied to bilateral "Zusanli"(ST 36)-"Yanglingquan"(GB 34) for 30 min,once daily for 2 t,2 w,3 w respectively.The paw withdrawal latency(PWL) was detected to be used as the pain threshold.Under deep anesthesia,the rat was decapitated for collecting blood samples.Plasma adrenocorticotropic hormone(ACTH),β-endorphine(EP),cortisone(COR) contents were detected using radioimmunoassay.Results: In comparison with control group,PWL difference values(PWLDV) of CCI+EA,OVX+CCI and OVX+CCI+EA groups increased significantly(P0.05),suggesting a marked decrease of pain threshold.Compared with CCI group,PWLDV of CCI+EA group at 3 w decreased significantly(P0.05),being close to normal control group(P0.05).Compared with OVX+CCI group,PWLDV of OVX+CCI+EA at 2 w and 3 w lowered significantly(P0.05),suggesting an evident pain relief.In comparison with CCI+EA group,PWLDV of OVX+CCI+EA group at most time courses were considerably higher(P0.05),showing a better cumulative analgesic effect in CCI rats without OVX.In CCI group,plasma β-EP increased slightly,ACTH had no clear changes,and COR lowered lightly at 2 t.No significant differences were found between control and CCI+EA groups in β-EP and ACTH levels at 2 w and 3 w(P0.05),only COR levels of CCI+EA group at 2 w and 3 w increased significantly(P0.05).Compared with control group,β-EP levels of OVX+CCI group at 2 w and 3 w increased significantly(P0.05);plasma ACTH had no marked changes(P0.05);COR contents of OVX+CCI group decreased evidently at 2 t and increased markedly at 2 w(P0.05).Compared with OVX+CCI group,in OVX+CCI+EA group,β-EP levels of 2 t and 2 w decreased significantly(P0.05);ACTH levels increased evidently at 2 t and 3 w,and decreased markedly at 2 w(P0.05);and COR level at 2 w decreased significantly(P0.05).It indicated that when cumulative EA analgesia appeared,in CCI animals,only plasma COR level increased pronouncedly,while in OVX+CCI rats,both plasma β-EP and COR contents decreased evidently.Conclusion: Both plasma β-EP and COR are involved in the accumulative analgesic effect of EA in the rat,and decline of learning memory ability may weaken the analgesic effect of EA to a certain degree,but no clear correlation tendency is found between changes of plasma β-EP and COR and the improvement of pain behavior.
【Fund】: 国家自然科学基金资助项目(C03050309)
【CateGory Index】: R245.97
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