Bevins R A, Ayres J J
University of Kentucky, Psychology Department, Lexington 40506-0044.
Pharmacol Biochem Behav. 1994 Sep;49(1):183-6. doi: 10.1016/0091-3057(94)90474-x.
Rats given a foot shock immediately after placement in a box subsequently freeze (immobility) much less in that box than rats given the same shock 2 min after placement. A possible explanation of this result is that these two procedures might induce different levels of opioid analgesia at the time of shock. Opioids might be present immediately after handling, transporting, and exposure to a new situation, but absent 2 min later. Two experiments examined this possibility by giving the opioid antagonist naloxone before conditioning (Experiment 1) or before conditioning and testing (Experiment 2). There was no effect of naloxone relative to saline controls. The results do not support the analgesia hypothesis. Experiment 2 precludes a stage-dependent learning account of the results.
被放入盒子后立即遭受足部电击的大鼠，相较于在放入盒子2分钟后遭受相同电击的大鼠，随后在该盒子中的僵住不动（静止）程度要低得多。对此结果的一种可能解释是，这两种程序在电击时可能会诱发不同程度的阿片类镇痛作用。在处理、运输以及接触新环境后，阿片类物质可能会立即出现，但在2分钟后则不存在了。两项实验通过在条件反射前（实验1）或在条件反射前及测试前（实验2）给予阿片类拮抗剂纳洛酮来检验这种可能性。与生理盐水对照组相比，纳洛酮没有产生影响。这些结果不支持镇痛假说。实验2排除了对结果的阶段依赖性学习解释。
