Day-night rhythms of opioid and non-opioid stress-induced analgesia: differential inhibitory effects of exposure to magnetic fields.
Day-night rhythms occurred in the naloxone-reversible (1.0 mg/kg), warm (opioid) and naloxone-insensitive, cold (non-opioid) swim stress-induced analgesia displayed by CF-1 mice. Maximum antinociceptive responses were evident at night, with the cold stress having significantly greater day- and night-time analgesic effects than the warm stress. An exposure for 30 min to a 0.5 Hz rotating magnetic field (1.5-90 gauss) reduced both the warm and cold stress-induced analgesia, with the magnetic stimuli having significantly greater inhibitory effects at night and on the opioid-induced responses. These results indicate that exposure to oscillating magnetic fields can significantly, and differentially, alter both opioid and non-opioid stress-induced analgesia and their day-night rhythms.
Kavaliers
Martin
M
Division of Oral Biology, Faculty of Dentistry, University of Western Ontario, London, Ont. N6A 5C1 Canada Department of Psychology, University of Western Ontario, London, Ont. N6A 5C1 Canada.
Ossenkopp
Klaus-Peter
KP
D000698:Analgesia; D000818:Animals; D002940:Circadian Rhythm; D004574:Electromagnetic Fields; D055590:Electromagnetic Phenomena; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D013312:Stress, Physiological; D013550:Swimming; D013696:Temperature
D009270:Naloxone; D009020:Morphine