Immobilization-induced analgesia: possible involvement of a non-opioid circulating substance.
Stress induced analgesia (SIA) and stress-induced changes in body temperature were studied in mice and rats. Immobilization was used as the stressor. Nociception was measured with the tail-flick method and body temperature was recorded in the colon. Within 5 min of immobilization a similar increase in tail-flick latencies was observed in the two species. Concomitantly, the body temperature increased in the rats and decreased in the mice. Transection of the spinal cord 7 days before the experiments tended to increase the effect of stress on the tail-flick latencies in both species. Pretreatment with naloxone HCL (2 mg/kg SC, 5 min before immobilization) did not influence SIA in either intact or spinal rats. Thus, analgesia induced by immobilization may be due to a non-opioid substance acting peripherally or reaching the spinal cord via the systemic circulation.
D000698:Analgesia; D000818:Animals; D001831:Body Temperature; D007103:Immobilization; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000097:blood / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000187:drug effects; D013116:Spinal Cord / Q000502:physiology
D009270:Naloxone