Methods Twenty-eight Wistar rats were randomly divided into ( 4 groups:) control group, morphine dependent group, morphine plus purine bases group and morphine plus purine nucleosides group, there were 7 rats per group. 方法:28只大鼠随机分成对照组、吗啡依赖组、吗啡依赖+嘌呤碱基组、吗啡依赖+嘌呤核苷组,每组7只。通过热敏感甩尾实验,记录大鼠热敏感甩尾潜伏期;