Presentation of a distractor speeds the decay of a pentobarbital-insensitive nonopioid hypoalgesia in rats
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Higher psychological/neural processes are thought to be involved in brief, but not long, shock-induced hypoalgesia. Researchers have shown that three brief (0.75-sec) tailshocks produce a hypoalgesia that is eliminated by spinalization, decerebration, pentobarbital anesthesia, and a post-shock distractor. In contrast, three long (25-sec) tailshocks produce a hypoalgesia that is eliminated by spinalization but not decerebration. Although it has been assumed that this hypoalgesia would survive pentobarbital anesthesia and exposure to a distracting stimulus, this has not been previously tested. Experiment 1 demonstrates that pentobarbital has no effect on long shock-induced hypoalgesia. Contrary to our expectations, this nonopioid hypoalgesia was attenuated by a postshock distractor (Experiment 2). This distractor effect appears to be opioid mediated because it was blocked by naltrexone (Experiment 3) and a low dose of morphine effectively substituted for the distractor (Experiment 4). The role of memorial processing in hypoalgesia is discussed. 1995, Psychonomic Society, Inc.. All rights reserved.
