Opiate antagonists and long-term analgesic reaction induced by inescapable shock in rats.

• DOI: 10.1037/h0077743
• Publication Date: 2006-06-08T02:38:50Z
• Authors: Steven F. Maier; Susan Davies; James W. Grau; Raymond L. Jackson; Daniel H. Morrison; Thomas Moye; John Madden; Jack D. Barchas
• Keywords: Electroshock; Dose-Response Relationship, Drug; Naloxone; Nociceptors; Naltrexone; Rats; 03 medical and health sciences; 0302 clinical medicine; Stress, Physiological; Receptors, Opioid; Reaction Time; Animals; Humans

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.