基于单一视觉线索建立大鼠吗啡条件性位置偏爱

目的:研究大鼠在单一视觉线索条件下是否能够形成吗啡条件性位置偏爱。方法:仅以训练箱体顶部的LED图案作为辨别和条件性刺激信号,采用剂量递增法对各组大鼠(吗啡-动态图案组、生理盐水-动态图案组、吗啡-静态图案组、生理盐水-静态图案组)进行条件性位置偏爱训练,训练周期分别为6 d和4 d,每天一个训练周期。吗啡-动态图案组和吗啡-静态图案组大鼠每天上午(或下午)给吗啡,在CPP箱伴药图案侧中停留45m in;下午(或上午)给生理盐水,在CPP箱非伴药图案侧中停留45 m in。吗啡的初始剂量为5 mg.kg-1,每2 d递增5 mg.kg-1。训练结束后的d1进行效果测试。生理盐水-动态图案组和生理盐水-静态图案组大鼠按同样操作,但一直给生理盐水,不给吗啡。结果:训练6 d后,吗啡-动态图案组大鼠在CPP箱体伴药图案侧停留的时间比生理盐水-动态图案组大鼠长(P<0.01),吗啡-静态图案组大鼠在CPP箱伴药图案侧停留的时间比生理盐水-静态图案组大鼠长(P<0.01)。在训练4 d的方案中,吗啡-动态图案组大鼠在CPP箱体伴药图案侧的停留时间则明显高于吗啡-静态图案组大鼠(P<0.05)。结论:大鼠在单一视觉线索下能够形成吗啡条件性位置偏爱,动态视觉线索较静态视觉线索更易使大鼠形成条件性位置偏爱。本实验可为药物成瘾领域中研究药物奖赏效应与条件刺激的关联机制提供一种新的方法学依据。

A PROTOCOL TO ESTABLISH RAT'S MORPHINE CONDITIONED PLACE PREFERENCE BASED ON SOLE VISUAL CUES

Objective:To study whether rats can develop conditioned place preference(CPP)under sole visual cue stimulation.Methods:The different images on LED screens on the top of the CPP box serve as discriminative and conditioned stimuli.Rats were trained with a dose-increasing manner in 6 or 4 training cycles(days).The dose of morphine initially was 5 mg·kg-1 and increased 5 mg·kg-1 after finishing every 2 training cycles.Rats were subjected into 4 groups:morphine paired by dynamic image(Mor_Dyn),saline paired by dynamic image(Sal_Dyn),morphine paired by static image(Mor_Sta),and saline paired by static image(Sal_Sta).In each training cycle(day),rats in Mor_Dyn and Mor_Sta groups received morphine injection and stayed in CPP box with intended image for 45 min in the morning(or afternoon)and received saline injection and stayed in CPP box with the control image for 45 min in the afternoon(or morning).Rats in Sal_Dyn and Sal_Sta groups followed the same operations but took saline instead of morphine.In the next day of last training,the efficacy of CPP establishment was tested.Results:With the 6 training-cycles(days)protocol,rats in Mor_Dyn group spent significantly more time in the morphine-paired side than rats in Sal_Dyn group(P<0.01);rats in Mor_Sta group spent significantly more time in the morphine-paired side than rats in Sal_Sta group(P<0.01);but neither the difference between Mor_Dyn group and Mor_Sta group nor the difference between Sal_Dyn group and Sal_Sta group was significant.With the 4 training-cycles(days)protocol,rats in Mor_Dyn group spent significantly more time in the morphine-paired side than rats in Mor_Sta group(P<0.05).Conclusion:Under the dynamic or the static visual cue stimulation,rats trained with morphine can develop CPP;dynamic image seems more effective than static image as visual conditioned stimulation.This study may provide a methodological precondition to study the subtle mechanism of the association between drug reward and conditioned visual cue.