目的　探讨褪黑素 (MT)对吗啡依赖小鼠免疫功能的影响及其与一氧化氮 (NO)的关系。方法　sc吗啡建立小鼠身体依赖模型 ;纳洛酮催瘾 ;称量免疫器官重量 ;ConA刺激的脾细胞淋巴增殖反应 ;碳粒廓清实验检测小鼠血中单核巨噬细胞的吞噬功能 ;小鼠腹腔巨噬细胞诱生NO含量的测定。结果　MT可对抗吗啡引起的免疫抑制 ,包括阻止吗啡对淋巴细胞增殖反应的抑制 ;明显提高吗啡依赖小鼠巨噬细胞的吞噬指数 ;抑制吗啡引起的腹腔巨噬细胞过量释放NO。MT对巨噬细胞的吞噬功能的增强作用可被纳洛酮阻断。结论　MT可提高吗啡依赖小鼠的免疫功能并抑制腹腔巨噬细胞中NO的过量释放 Objective To investigate the effect of melatonin (MT) on immune function in morphine dependent mice and its relationship with nitric oxide (NO). METHODS Sc morphine was used to establish a mouse model of body dependence. Naloxone was added to the model. Immune organ weights were weighed. ConA-stimulated splenocyte lymphocyte proliferation reaction was performed. The phagocytic function of monocyte-macrophage Determination of NO content in murine peritoneal macrophages. Results MT could antagonize the morphine-induced immunosuppression, including inhibiting the inhibition of morphine on lymphocyte proliferation; significantly increasing phagocytic index of morphine-dependent mouse macrophages; and inhibiting overproduction of NO by morphine-induced peritoneal macrophages. The enhanced effect of MT on the phagocytosis of macrophages can be blocked by naloxone. Conclusion MT can enhance the immune function of morphine dependent mice and inhibit the excessive release of nitric oxide in peritoneal macrophages