本世纪七十年代初

Simon

Pert和 Terenius 三个实验室分别独立地确定在体内特别是中枢神经系统内存在着特异的阿片受体。随后

Hughes 等成功地从猪脑中分离提取出两种具有阿片活性的五肽—甲硫-脑啡肽和亮-脑啡肽。在此以后

人们又从垂体中发现了阿片活性更强的β-内啡肽和强啡肽。这些内源性阿片样物质(OLS)的发现

为疼痛生理之研究打开了新的突破口.1975年

Mayer 等首次报告了静脉内注射特异的阿片受体阻断剂纳络酮可以翻转针刺的镇痛作用.这就提示在针刺镇痛的机制中可能有 OLS 参与

但尚不能明确在OLS 这一族化合物中哪一个具体组分在发挥作用.The finding that acupuncture analgesia could be blocked by naloxone

the stereospecific antagonist of opiate receptors

provided ample evidence for the participation of endogenous opiate-like substances(OLS)in medi- ating the effect of acupuncture analgesia.However it gave no clue as to which member of the OLS family was actually involved. Taking the advantages of the high specificity of antibody-antigen bin- ding

we have injected the IgG fraction of the rabbit antiserum against human β-endorphin(β-EP IgG)into the periaqueductal grey(PAG)or the subara- ehnoid space of the lumbar spinal cord to see its effect on electroacupunc- ture(EA)analgesia and morphine analgesia. Rabbits were equipped with stainless steel cannulae of o.d.0.7mm directed to both sides of the PAG

or with PE-10 tubing indwelled via foramen magnum down to L 3-4.At least one week was allowed for reco- very from surgical operation.The site of injection was verified by eryostat sections at the termination of the experiment. For intra-PAG injection the total volume used was 4μl to be finished within 8 minutes

containing normal serum IgG(15μg)

β-EP IgG(15μg)or β-EP(5μg).For intrathecal injection:70μl was injected within 3 minutes

containing normal serum IgG(30μg)

β-Ep IgG(45μg)or β-EP(30μg).EA of 2-15Hz

1V for 10 minutes was given 10 minutes after the starting of the microinjection and the effect of EA analgesia was determined by the per cent change of the pain threshold as asessed by the latency of the avoidence reaction induced by the radiant heat applied on the skin over the muzzle or the tail.In some experiments morphine HCl

4mg/kg

was injected i.v.instead of EA stimulation.Serum preparations were provided by Professor L.Terenius and R.Folkesson

Uppsala University

Sweden shipped in pairs with one antiserum and one control serum in coded man- ner.The code was brocken when the experiment was finished.Eight to 12 rabbits were used for each expsrimental group. The results of the experiments showed that intra-PAG injection of 5 and 15μg of β-EP IgG attenuated the effect of EA analgesia by 20 and 55%(P<0.01).Intrathecal injection of 45μg of β-EP IgG

however

exhi- bited no significant effect on EA analgesia whether it was assessed on the head or on the tail region.The analgesic effect of morphine was not sign- ificantly affected by micr0injection of β-EP IgG into PAG or spinal cord. microinijection of 5μg of β-EP into PAG increased the pain threshold by 820%

an effect comparable to that of 10μg of morphine.However

no significant change on the pain threshold of the head or the tail was en- countered after intrathecal injection of 30μg of β-Ep

which was 6 times as big as the dose effective in PAG area. The data indicate that immuno-reactive β-EP is an important mediator for EA analgesia in PAG area

but not in the spinal cord.In compatible with this is the finding that no β-Ep was found in the spinal cord as de- tected by radioimmunoassay or immunohistochemical examinations.