家兔中脑导水管周围灰质内注射抗β-内啡肽抗体削弱电针镇痛效果

<正> 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.

ELECURO-ACUPUNCTURE ANALGESIA IN THE RABBIT WAS PARTIALLY BLOCKED BY ANTI-β-ENDORPAIN ANTISERUM INJECTED INTO PERIAQUEDUCTAL GREY,BUT NOT BY ITS INTRATHECAL INJECTION

The finding that acupuncture analgesia could be blocked by naloxone,the stereospecific antagonist of opiate receptors,provided ample evidencefor the participation of endogenous opiate-like substances(OLS)in medi-ating the effect of acupuncture analgesia.However it gave no clue as towhich 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 humanβ-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.0.7mmdirected to both sides of the PAG,or with PE-10 tubing indwelled viaforamen 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 eryostatsections at the termination of the experiment.For intra-PAG injection the total volume used was 4μl to be finishedwithin 8 minutes,containing normal serum IgG(15μg),β-EP IgG(15μg)orβ-EP(5μg).For intrathecal injection:70μl was injected within 3 minutes,containing normal serum IgG(30μg),β-Ep IgG(45μg)or β-EP(30μg).EAof 2-15Hz,1V for 10 minutes was given 10 minutes after the starting ofthe microinjection and the effect of EA analgesia was determined by theper cent change of the pain threshold as asessed by the latency of theavoidence reaction induced by the radiant heat applied on the skin overthe muzzle or the tail.In some experiments morphine HCl,4mg/kg,wasinjected i.v.instead of EA stimulation.Serum preparations were providedby Professor L.Terenius and R.Folkesson,Uppsala University,Swedenshipped in pairs with one antiserum and one control serum in coded man- ner.The code was brocken when the experiment was finished.Eight to 12rabbits were used for each expsrimental group.The results of the experiments showed that intra-PAG injection of 5and 15μg of β-EP IgG attenuated the effect of EA analgesia by 20 and55%(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 thehead 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 thresholdby 820%,an effect comparable to that of 10μg of morphine.However,nosignificant 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 asbig as the dose effective in PAG area.The data indicate that immuno-reactive β-EP is an important mediatorfor EA analgesia in PAG area,but not in the spinal cord.In compatiblewith this is the finding that no β-Ep was found in the spinal cord as de-tected by radioimmunoassay or immunohistochemical examinations.