Linseman M A, Harding S
Biobehavioral Research Department, Addiction Research Foundation, Toronto, Canada.
Psychopharmacology (Berl). 1989;97(1):103-7. doi: 10.1007/BF00443422.
Weight restriction has frequently been used to induce consumption of pharmacologically significant amounts of alcohol by rats. When previously weight-restricted rats are fed ad lib., however, their alcohol consumption is substantially reduced. This could occur because weight restriction per se causes increased alcohol consumption, or because the stimulus conditions (in this case, largely interoceptive) that were originally associated with drinking have changed, resulting in a stimulus generalization decrement. The present experiment was designed to discriminate between these two possibilities. Two groups of animals, one at free-feeding weight (FFW) and one at 80% FFW were initially trained to drink alcohol in a limited access paradigm. Each group was then divided into two, such that one half remained at its original weight and the other was gradually shifted to the reverse feeding condition in a double cross-over design. When alcohol consumption was again stable the experimental groups were returned to their original weights. If the weight restriction hypothesis were true, animals should drink more when weight-reduced and less when at FFW. According to the stimulus generalization decrement hypothesis, drinking should decrease with any shift from their initial weight. The direction of the results was such as to support the weight restriction hypothesis, but the magnitude of the changes was greater than would be expected on the basis of the respective control groups, and the effects were often transient. In these ways the results more closely resembled positive and negative contrast effects that have traditionally been described following shifts in amount of reinforcement. Possible mechanisms and the importance of an animal's history as a determinant of alcohol consumption are discussed.
限重常被用于诱导大鼠摄入药理学上显著量的酒精。然而，当先前限重的大鼠改为自由进食时，它们的酒精摄入量会大幅减少。出现这种情况可能是因为限重本身导致酒精摄入量增加，或者是因为最初与饮酒相关的刺激条件（在这种情况下，主要是内感受性的）发生了变化，从而导致刺激泛化递减。本实验旨在区分这两种可能性。两组动物，一组处于自由进食体重（FFW），另一组处于80%FFW，最初在有限接触范式中接受饮酒训练。然后每组再分为两组，使得一半保持其原始体重，另一半在双交叉设计中逐渐转变为反向进食条件。当酒精摄入量再次稳定时，实验组恢复到其原始体重。如果限重假说正确，动物体重减轻时应饮用更多酒精，体重处于FFW时应饮用更少酒精。根据刺激泛化递减假说，饮酒量应随与初始体重的任何变化而减少。结果的方向支持限重假说，但变化幅度大于基于各自对照组预期的幅度，且影响往往是短暂的。通过这些方式，结果更类似于传统上在强化量变化后所描述的正性和负性对比效应。讨论了可能的机制以及动物经历作为酒精消费决定因素的重要性。
