Stewart R B, Grupp L A
Department of Pharmacology, University of Toronto, Canada.
Pharmacol Biochem Behav. 1989 Feb;32(2):431-7. doi: 10.1016/0091-3057(89)90175-5.
A previous experiment has shown that rats will avoid environmental cues that have been associated with a history of ethanol self-administration. One possible explanation for this conditioned place aversion may be related to the temporal parameters of that experiment. During the initial segment of each 90-min conditioning/drinking trial (when most of the drinking occurred) the blood ethanol levels (BELs) were low and may well have produced positive effects at that time. However, as the drug continued to be absorbed and BELs increased during the remainder of the 90-min trial, the final (and conditioned) drug effects may have been aversive. In the present experiment the trial length was shortened to a 15-min period so that only low BELs would be temporally paired with the conditioning environment. A conditioned preference for that environment was predicted. Twelve rats were trained to self-administer ethanol in one environment and had water available in a different environment. Eight control animals had only water in both environments. BELs were measured and found to be low (16.8 to 57.6 mg%) and rising during the conditioning trials. However, when given a choice between the two environments, the rats avoided the environment in which they formerly consumed ethanol. No change in preference was noted for the control animals. This result was in accordance with previous findings but did not support the hypothesis that low, excitatory BELs would mediate a conditioned place preference in the rat.
先前的一项实验表明，大鼠会避开与乙醇自我给药历史相关的环境线索。这种条件性位置厌恶的一种可能解释可能与该实验的时间参数有关。在每次90分钟的条件化/饮水试验的初始阶段（大部分饮水发生在此期间），血液乙醇水平（BELs）较低，此时很可能产生了积极影响。然而，随着药物在90分钟试验的剩余时间内持续吸收且BELs升高，最终（以及条件化的）药物效应可能是厌恶的。在本实验中，试验时长缩短至15分钟，以便只有低BELs会在时间上与条件化环境配对。预计会对该环境产生条件性偏好。12只大鼠在一个环境中被训练自我给药乙醇，在另一个环境中有水可供饮用。8只对照动物在两个环境中都只有水。测量了BELs，发现在条件化试验期间其较低（16.8至57.6毫克%）且在上升。然而，当在两个环境之间进行选择时，大鼠避开了它们先前饮用乙醇的环境。对照动物的偏好没有变化。这一结果与先前的发现一致，但不支持低水平、具有兴奋性的BELs会介导大鼠条件性位置偏好的假设。
