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家兔伏核注射吗啡引起的镇痛可被中脑导水管周围灰质注射纳洛酮或甲啡肽抗体所阻断

于龙川, 石玉顺, 韩济生

北京医科大学生理教研室. 北京

摘要

本实验室以往的资料表明,在家兔中脑导水管周围灰质(PAG)到伏核之间存在一条与镇痛有夫的神经通路,该通路以5-羟色胺(5-HT)和甲啡肽(ME)为其递质。本工作进一步探讨从伏核到PAG的下行镇痛通路。以辐射热照射家兔嘴侧部皮肤,测量其躲避反应的潜伏期(ERL)作为痛反应阈,简称痛阈。通过预先埋植的慢性套管向伏核内微量注射吗啡,20min后向PAG内双侧注射纳洛酮(NX)或脑啡肽抗血清,观察ERL的变化。(1)伏核内注射吗啡20μg/1μl,引起ERL升高80％以上,作用持续50min以上。

关键词： 伏核; 导水管周围灰质(PAG); 吗啡; 纳洛酮; 甲啡肽抗血清; 中脑边缘镇痛回路

Analgesia induced by morphine administered to the nucleus accumbens was blocked by naloxone of [Met~(5)] enkephalin antiserum injected into the periaqueductal grey of the rabbit

Yu Longchuan, Shi Yushun, Han Jisheng

Department of Physiology, Beijing Medical University. Beijing, China

Abstract

We have shown in rabbits an ascending neuronal pathway of analgesia from
periaqueductal grey (PAG) to the nucleus accumbens, using 5-hydroxytryptamine (5-HT) and [Met~(5)] enkephalin (ME) as neurotransmitters.The present study was performed to explore the possible existence of a descending analgesic
pathway from nucleus accumbens to PAG.Pain threshold was measured by the latency of the escape response (ERL) to radiant heat applied on the skin of the snout. Rabbits equipped with chronic intracranial cannulae were given morphine into nucleus accumbens to induce analgesia, which was followed microinjection of naloxone or antiserum against enkephalin into PAG 20 min later. It was found that injection of morphine,20#mu#g/1#mu#l, into nucleus accunbens produced an increase in ERL over 80%, lasting for a period of more than 50 min. This effect of morphine was partially blocked by naloxone administered to PAG in a dose-ependent manner (0.5,1.0,2.0#mu#g/#mu#l/site). A statistically significant blockade of the morphine analgesia was also achieved by intra-PAG injection of antiserum against ME (1#mu#l/site), but not by the same amount of normal rabbit serum or antiserum against [Leu~(5)] enkephalin. These results suggest the existence of a descending pathway of analgesia from nucleus accumbens to PAG, using ME as neurotransmitter in the PAG area. This descending pathway of analgesia, in connection with the ascending pathway from PAG to nucleus accumbens, may form a meso-limbic loop of analgesia. The implication of the possible existence of the neuronal loop in acupuncture analgesia and morphine analgesia is discussed.

Key words: Nucleus accumbens;Periaqueductal grey (PAG);Morphine;Naloxone;[Met_(5)] enkephalin antiserum;Meso-limbic loop of analgesia

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引用本文：

于龙川, 石玉顺, 韩济生. 家兔伏核注射吗啡引起的镇痛可被中脑导水管周围灰质注射纳洛酮或甲啡肽抗体所阻断[J]. 生理学报 1987; 39 (4): .

Yu Longchuan, Shi Yushun, Han Jisheng. Analgesia induced by morphine administered to the nucleus accumbens was blocked by naloxone of [Met~(5)] enkephalin antiserum injected into the periaqueductal grey of the rabbit. Acta Physiol Sin 1987; 39 (4): (in Chinese with English abstract).