Maier S F
Department of Psychology, University of Colorado, Boulder 80309.
Behav Neurosci. 1989 Feb;103(1):131-43. doi: 10.1037//0735-7044.103.1.131.
Factors that determine whether naltrexone and pentobarbital anesthesia block the hypoalgesia produced by electric shock were investigated. The number of shocks delivered, the time since the last shock, and whether the subject is removed from the shock environment for testing were all found to be critical. One shock was followed by an initial hypoalgesia that was reversed by naltrexone but was not affected by pentobarbital. Moreover, this initial hypoalgesia was not eliminated by removing the subject from the shock apparatus. When testing was conducted in the shock context, this early hypoalgesia was followed by a hypoalgesia that was still reversed by naltrexone but differed from the early response in that it was eliminated by pentobarbital anesthesia. This second hypoalgesia did not occur when testing was conducted after removing the animal from the shock apparatus. Five shocks were also followed by two separable responses. Here the first response was also not reduced by pentobarbital, but it was not blocked by naltrexone. This initial response was also not prevented by removal from the shock context, but, again, the second response did not occur after removal. The pattern after 80 shocks was quite different. Here the hypoalgesic response did not appear to change in character across the 10 min of testing or with removal from the shock apparatus. The response persisted for 10 min in the shock context or after removal and was blocked by both naltrexone and pentobarbital throughout its entire duration. These results reconcile findings from different laboratories and bear on a number of theoretical models of stress-induced hypoalgesia.
研究了决定纳曲酮和戊巴比妥麻醉是否能阻断电击所致痛觉减退的因素。结果发现，电击次数、距上次电击的时间以及是否将实验对象移出电击环境进行测试均至关重要。一次电击后会出现初始痛觉减退，这种痛觉减退可被纳曲酮逆转，但不受戊巴比妥影响。此外，将实验对象从电击装置中移出并不能消除这种初始痛觉减退。当在电击环境中进行测试时，这种早期痛觉减退之后会出现另一种痛觉减退，它仍可被纳曲酮逆转，但与早期反应不同的是，它可被戊巴比妥麻醉消除。将动物从电击装置中移出后进行测试时，这种第二种痛觉减退不会出现。五次电击后也会出现两种可分离的反应。这里的第一种反应同样不受戊巴比妥影响，但不能被纳曲酮阻断。这种初始反应也不会因移出电击环境而被阻止，但同样，第二种反应在移出后不会出现。80次电击后的模式则大不相同。在这里，在10分钟的测试过程中或从电击装置中移出后，痛觉减退反应的性质似乎没有改变。该反应在电击环境中或移出后持续10分钟，并且在整个持续时间内都被纳曲酮和戊巴比妥阻断。这些结果调和了不同实验室的研究发现，并与一些应激诱导痛觉减退的理论模型相关。
