Cunningham C L, Henderson C M
Department of Behavioral Neuroscience and Portland Alcohol Research Center, The Oregon Health Sciences University, 97201-3098, USA.
Behav Pharmacol. 2000 Nov;11(7-8):591-602. doi: 10.1097/00008877-200011000-00006.
Previous studies have shown that ethanol produces conditioned place preference (CPP) in mice when injections are given immediately before exposure to the conditioned stimulus (CS). Paradoxically, however, injection of ethanol immediately after the CS produces conditioned place aversion (CPA). Four experiments were conducted to characterize the parametric boundaries of CPA produced by post-CS ethanol exposure. Experiment 1 showed that CPA is positively related to ethanol dose, with significant CPA at 2 and 4 g / kg, but not at 1 g / kg. Experiment 2 revealed an inverse relationship between CPA and trial duration, i.e. significant CPA occurred when the trial duration was 5, 15 or 30 min, but not when it was 60 or 90 min. Experiment 3 indicated that ethanol pre-exposure (eight daily injections) significantly reduced subsequent development of CPA. Finally, experiment 4 showed that repeated exposure to the CS alone (six 30 min exposures to each CS) after CS-ethanol pairings produced complete extinction of CPA. The same extinction procedure also completely eliminated CPP induced by pre-CS injections of ethanol. Overall, these studies demonstrate that CPA induced by post-CS ethanol injection is influenced by many of the same variables that affect CPP produced by pre-CS ethanol injection in mice. However, these findings do not resolve the issue of whether the 'before-versus-after' effect in ethanol place conditioning is better explained by assuming ethanol produces only rewarding effects or by assuming that ethanol produces both rewarding and aversive effects.
先前的研究表明，在小鼠接触条件刺激（CS）之前立即注射乙醇会产生条件性位置偏爱（CPP）。然而，矛盾的是，在CS之后立即注射乙醇会产生条件性位置厌恶（CPA）。进行了四项实验来描述CS后乙醇暴露所产生的CPA的参数边界。实验1表明，CPA与乙醇剂量呈正相关，2 g / kg和4 g / kg时会产生显著的CPA，但1 g / kg时不会。实验2揭示了CPA与试验持续时间之间呈反比关系，即当试验持续时间为5、15或30分钟时会出现显著的CPA，但60或90分钟时则不会。实验3表明，乙醇预暴露（每日注射八次）显著降低了随后CPA的发展。最后，实验4表明，在CS-乙醇配对后，单独重复暴露于CS（每次CS暴露30分钟，共六次）会使CPA完全消退。相同的消退程序也完全消除了CS前注射乙醇所诱导的CPP。总体而言，这些研究表明，CS后注射乙醇所诱导的CPA受到许多与影响小鼠CS前注射乙醇所产生的CPP相同的变量的影响。然而，这些发现并未解决在乙醇位置条件反射中“之前与之后”效应是通过假设乙醇仅产生奖赏效应还是通过假设乙醇产生奖赏和厌恶效应来更好地解释这一问题。
