纳洛酮对不同强度电针所致镇痛效应的作用

<正> 脑内阿片受体及内啡肽系统的发现,对针刺镇痛原理研究提供了新的线索,关于针刺所致各种效应,特别是镇痛效应和阿片受体及其递质系统有何关系的问题,引起人们广泛的兴趣。Mayer 和上海市人体针刺镇痛实验协作组分别在人体用吗啡拮抗剂—纳洛酮阻断了针刺镇痛效应。然而动物实验的结果却存在分歧,Pomerang 报导纳洛酮能明显拮抗小鼠的电针镇痛作用;上

THE EFFECTS OF NALOXONE ON ACUPUNCTURE ANALGESIA PRODUCED BY DIFFERENT STRENGTH OF ELECTRIC STIMULATION

It is reported in this paper that naloxone 0.4mg/Kg intravenously signi-ficantly antagonized the analgseic effect of moderate strength elecroacupuncturebut did not antagonize superstrength electro-acupuncture.In forty nine rabbits,ipsilateral “He-Gu” and “Wai Guan” were electri-cally needled.The frequency of the electric stimulaton was 2-4 c/s,and theanimals were divided into two groups according to the strength of stimulat-ion:1.The moderate strength electro-acupuncture group animals were givenelectro-acupuncture with electric current of 7.5-8.0mA.The stimulations weresufficient to cause moderate muscle contration but mild enough to keep theanimals in quiet state.2.The superstrength electro-acupuncture group ani-mals were treated with a superstrength(12.5-15 mA)electro-acupuncture asa stress stimulation.The animals showed agitation and struggled hard.Rabbits with more than two-fold rise of pain threshold at the 20th minute after electro-acupuncture were conidered as “acupuncture effective”and werechosen for further studies.The acupuncture group and the superstrength acu-puncture group were 70% and 66% respectively,and the raised percentagesof pain threshold in these two groups were also withot any statistic differ-ence.At the 20th min.after acupuncture,part of the animals of these twogroups were given naloxone 0.4mg/Kg intrevenously,and the others weregiven normal saline.It was found that the analgesic effects of moderatestrength acupuncture were markedly reversed by naloxone in 10 out of 14animals.The total decrease rate at the 5th min.after naloxone was 41%which significantly differed fnom that in the saline group(P<0.005).Thereversed pain threshold then rose again gradually and nearly reached thepre-injection level 15 min.after naloxone.In the meantime,the analgesiceffects of superstrength acupuncture were not reversed by naloxone.Therewas only 1 out of 10 animals showed a decreased pain threshold at the 5thmin.after naloxone,the average pain threshold at that time was not statis-tically different from that before naloxone.The pain threshold of the saline group and the naloxone group remainedstable.The present experiment suggests that the analgesic effect of moderatestrength acupuncture results partially from the activity of opiate receptors,and its mechanism differs at least in some aspects from that of “stress anal-gesia”