Opiate antagonists and long-term analgesic reaction induced by inescapable shock in rats.
Five experiments examined the influence of opiate antagonists on both the short-term analgesic reaction resulting 30 min after exposure to inescapable shock and the long-term analgesic reaction resulting after reexposure to shock 24 hr after inescapable shock exposure. Experiment 1 showed that the long-term analgesic reaction could be reduced by administration of naltrexone prior to exposure to inescapable tail shock. Experiment 2 showed that the reduction in the long-term analgesic reaction produced by naltrexone was dose-dependent. Experiment 3 showed that the long-term analgesic reaction could also be reduced by administration of naltrexone prior to reexposure to shock. Experiment 4 showed that the long-term analgesic reaction could be reduced by administration of large dose of naloxone prior to reexposure to shock. Experiment 5 showed that the short-term analgesic reaction was reduced by naltrexone administered prior to inescapable shock. Some implications of these results for the biochemical substrates of both learned helplessness and stress-induced analgesia are discussed.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004597:Electroshock; D006801:Humans; D009270:Naloxone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009271:Naltrexone / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011930:Reaction Time / Q000187:drug effects; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D013312:Stress, Physiological / Q000503:physiopathology*
D011957:Receptors, Opioid; D009270:Naloxone; D009271:Naltrexone