PRESENTATION OF A DISTRACTOR SPEEDS THE DECAY OF A PENTOBARBITAL-INSENSITIVE NONOPIOID HYPOALGESIA IN RATS

Higher psychological/neural processes are thought to be involved in br ief, but not long, shock-induced hypoalgesia. Researchers have shown t hat three brief(0.75-sec) tailshocks produce a hypoalgesia that: is el iminated by spinalization, decerebration, pertobarbital anesthesia, an d a postshock distracter. In contrast, three long (25-sec) tailshocks produce a hypoalgesia that is eliminated by spinalization but not dece rebration. Although it has been assumed that this hypoalgesia would su rvive pentobarbital anesthesia and exposure to a distracting stimulus, this has not been previously tested. Experiment 1 demonstrates that p entobarbital has no effect on long shock-induced hypoalgesia. Contrary to our expectations, this nonopioid hypoalgesia was attenuated by a p ostshock distractor (Experiment 2). This distracter effect appears to be opioid mediated because it was blocked by naltrexone (Experiment 3) and a low dose of morphine effectively substituted for the distracter (Experiment 4). The role of memorial processing in hypoalgesia is dis cussed.