Whitehouse W G, Blustein J E, Walker J, Bersh P J, Margules D L
Behav Neurosci. 1985 Aug;99(4):717-33. doi: 10.1037//0735-7044.99.4.717.
Rats exposed to inescapable shock exhibited analgesia and a significant impairment of shock-escape learning in a shuttle box situation 24 hr later. In contrast, rats exposed to escapable shock or to no shock displayed neither effect. Naltrexone (10 mg/kg) significantly reduced the analgesia and completely eliminated the escape deficit in inescapably shocked rats but induced hyperalgesia, coupled with a marked deterioration of escape performance, in escapably shocked and nonshocked rats. The same dose of quaternary naltrexone, which has low ability to cross the blood-brain barrier, had no effect on either the antinociception or the escape deficit produced by inescapable shock, although it also induced escape impairment and hyperalgesia in rats preexposed to escapable shock or to no shock. A second experiment demonstrated that both the escape interference and the antinociceptive consequences of prior inescapable shock could be reduced partially by a much lower dose (1 mg/kg) of naltrexone but 50 times this amount of quaternary naltrexone was still without effect. These results imply that the consequences of exposure to inescapable shock are mediated by activation of central opioid processes whereas naltrexone-induced effects in escapably shocked and nonshocked animals may be peripherally mediated. The relevance of these findings to the possible role of nociception in escape performance is discussed.
暴露于不可逃避电击的大鼠在24小时后在穿梭箱实验中表现出镇痛作用以及逃避电击学习能力的显著受损。相比之下，暴露于可逃避电击或无电击的大鼠均未表现出这些效应。纳曲酮（10毫克/千克）显著减轻了不可逃避电击大鼠的镇痛作用，并完全消除了其逃避缺陷，但在可逃避电击和未电击的大鼠中却诱导了痛觉过敏，同时伴有逃避行为的明显恶化。相同剂量的季铵型纳曲酮穿过血脑屏障的能力较低，对不可逃避电击产生的抗伤害感受或逃避缺陷均无影响，尽管它也会在预先暴露于可逃避电击或未电击的大鼠中诱导逃避障碍和痛觉过敏。第二项实验表明，较低剂量（1毫克/千克）的纳曲酮可部分减轻先前不可逃避电击对逃避行为的干扰和抗伤害感受后果，但50倍于此剂量的季铵型纳曲酮仍然无效。这些结果表明，暴露于不可逃避电击的后果是由中枢阿片样物质过程的激活介导的，而纳曲酮在可逃避电击和未电击动物中诱导的效应可能是由外周介导的。本文讨论了这些发现与伤害感受在逃避行为中可能作用的相关性。
