我们曾经报告

给大鼠反复、间断电针可以使针效逐渐下降以至消失

即产生电针耐受。本工作进一步证明

应用持续长时间电针

也可引起大鼠电针耐受.并观察了持续电针所致耐受发生、发展和恢复的规律及其与吗啡的交叉耐受现象.方法【测痛和电针】实验用160～220克雌性大鼠

固定于特制固定器内

以辐射热-甩尾法进行测痛

实验开始时连续测痛三次

每次间隔5分钟

取三次测痛的均值为基础痛阈。电针穴位取双侧“足三里”和“三阴交”

以国产57-6型电针仪给予疏密式脉The course of development and disappearance of tolerance to continuous electroacupuncture(EA)was studied in rats. 1.Development of AT in continuous EA:It was found that EA(2- 15Hz

3v)for 10 min brought about an increase of tail flick latency by 133+8%(mean+SEM).However there was a gradual decrease in EA effect following prolonged EA stimulation

indicating that continuous EA would induce acupuncture tolerance(AT).Increasing the intensity of EA from 3v to 6v and 9v

the EA effect on the AT rats was still muchlower than the corresponding values in control group.After the cessation of 6h EA sti- mulation the rats were found to resume their original EA effect in 32 hours. 2.The effect of AT on morphine analgesia:The results of giving a testing dose of morphine(6mg/kg

s.c.)to AT rats indicated that the anal- gesic effect of morphine decreased along with the development of AT and then recovered along with the recovery of E.A.analgesia.The relation between morphine analgesia(Y)and EA analgesia(X)could be described in a regr- ession equation:Y=0.57X+41.7

r=0.93

p<0.01 3.The effect ot MT on EA analgesia:EA(3v

10 min)was applied to MT (Morphine Telerarnce)rats.The results showed that the analgesic effect of EA decreased along with the development of MT and recovered along with the reco- very of morphine analgesia.A positive correlation was found between EA an- algesia(Y)and morphine analgesia(X)(Y=0.85X+22.9

r=0.97

p<0.01). Compared with the intermittent EA

continuous EA will lead to the development of AT in a shorter period and to a deeper extent.The bidirec- tional partial cross tolerance between EA analgesia and morphine analgesia suggests a similar

although not identical

underlying mechanism between these effects.