吗啡行为及条件性行为敏感化效应及其个体差异

目的：考察吗啡处理下，大鼠行为敏感化及条件性行为敏感化效应及其个体差异性表现。方法：根据大鼠在初次抵达的新颖环境中水平活动量的高低，将大鼠划分为高反应大鼠（High responder, HR）和低反应大鼠（Low responder, LR），应用自动监测大鼠活动箱，分别考察HR和LR大鼠在行为及条件性行为敏感化效应表达上的差异。结果：（1）连续5天吗啡给药，LR大鼠活动量显著升高，HR大鼠无此效应；（2）条件测试日（第6天），给药与环境匹配大鼠，活动量较给药与环境非匹配组动物和对照组动物显著为高；此效应在HR和LR大鼠同时存在；（3）从给予吗啡到给予盐水，发现LR大鼠活动量显著下降，而HR大鼠活动量无显著改变。结论：在连续给药下，LR大鼠较HR大鼠，在行为敏感化效应的形成中，具有更为显著的效应，此效应为LR动物对吗啡更高的药物效应，而非条件效应所致，同时HR和LR大鼠都可以对吗啡条件性线索产生应答，产生条件性行为敏感化效应。

UNCONDITIONED AND CONDITIONED BEHAVIORAL SENSITIZATION OF REPEATED MORPHINE ADMINISTRATION:AN INDIVIDUAL DIFFERENCE STUDY IN RATS

Behavioral sensitization has been defined as progressive increase of the rewarding and reinforcing effect of drugs of abuse, which has been considered to underlie the etiology of drug craving and relapse. Aim: To explore morphine behavioral sensitization and its conditioned effect, with further investigation into potential individual difference manifestation. Method: Rats were characterized as high and low responders (HR vs. LR) via initial motor activity developed in an inescapable chamber. By using computer-interfaced monitoring system, the locomotor activities of rats were observed under 5-day successive drug treatment to test the development of morphine sensitization. Then a saline challenge was given on day 6 to test its conditioned effect. Results: 1: LR rats expressed increased locomotor activities while HR rats were without this effect upon repeated morphine exposure. 2: Rats successively with drug treatment in the test chamber (paired group) expressed heightened motor activity compared with unpaired and control group upon saline challenge. This effect existed in both HR and LR group. 3: Locomotor activity from toward drug to saline treatment significantly decreased in LR but not in HR rats. Conclusion: 1: Under successive drug treatment, LR, other than HR rats developed morphine behavior sensitization. 2: Both HR and LR rats possessed the capability to develop conditioned behavioral sensitization toward morphine. 3: LR rats responded more strongly than HR rats to drug treatment.