褪黑素对吗啡依赖小鼠的作用及其与脑啡肽关系的研究

目的观察褪黑素（ＭＴ）对吗啡（Ｍｏｒ）致依赖性的作用及机制分析。方法连续ｉｐＭｏｒ与纳络酮催促建立小鼠依赖模型，甩尾法，淋巴细胞增殖反应和脑啡肽（Ｍｅｔ－Ｅｎｋ）放免测定。结果Ｍｏｒ依赖组小鼠痛阈下降，跳跃次数增加，肛温降低，伴有胸腺细胞增殖能力的低下，Ｍｏｒ依赖小鼠的脑和血浆Ｍｅｔ－Ｅｎｋ亦明显降低。本文首次发现ｉｇＭＴ（３０、９０ｍｇ·ｋｇ－１×７ｄ）能明显提高依赖性小鼠的痛阈，减少跳跃次数，恢复其肛温，阻止Ｍｏｒ对淋巴细胞功能的抑制，并能维持脑、血浆Ｍｅｔ－Ｅｎｋ接近正常对照水平。结论ＭＴ具有对抗Ｍｏｒ致小鼠依赖性作用，其机制与维持内源性Ｍｅｔ－Ｅｎｋ水平有关。

Effects of melatonin on morphine induced mice dependence and relation with enkephalin

AIM To observe the effects and mechanisms of melatonin (MT) on morphine (Mor) induced mice dependence. METHODS The Mor dependent mice model was established by intraperitoneal (ip) administered Mor (10 mg·kg-1) for seven days and the pain threshold, thymocyte proliferation and methionine enkephalin(Met Enk) were determined by the tail flick, cell incubation and radioimmunoassay, respectively. RESULTS The pain threshold and the thymocytes proliferation in Mor dependent mice were all decreased, and there were a marked increase in jumping number and a marked decrease in rectal temperature after naloxone (Nal) precipitation. The results also showed that the brain and plasma Met Enk levels were lower in Mor dependent mice. MT(30,90 mg·kg-1,ig×7 d) could significantly antagonized the effects induced by Mor and maintained the brain and plasma Met Enk levels to normal status. CONCLUSIONS MT could antagonize the Mor induced mice dependence, which was related to its maintaining the levels of endogenous Met Enk.