Intermittent cold water stress-analgesia in rats: cross-tolerance to morphine

Pharmacol Biochem Behav. 1984 Apr;20(4):631-3. doi: 10.1016/0091-3057(84)90315-0.


Continuous cold water swim ( CCWS , 3.5 min, 2 degrees C) induces a non-opiate type of analgesia since 14 mg/kg of naltrexone or 20 mg/kg of naloxone only partially antagonize this stress-induced analgesia (SIA) and since there is no cross-tolerance between CCWS and morphine-analgesia. Intermittent cold water swim ( ICWS ) analgesia is significantly antagonized by naltrexone (14 mg/kg). These studies suggested that CCWS -analgesia is mediated by non-opioid systems, while ICWS -analgesia acts through a system that also mediates morphine analgesia. The hypothesis that ICWS -analgesia shares a common opioid pathway with morphine-analgesia, but not with CCWS -analgesia, was further tested by cross-tolerance studies in rats. The results showed a complete cross-tolerance to morphine analgesia in ICWS -tolerant animals,, but no cross-tolerance in animals. This suggests that morphine- and ICWS -analgesia partially share a common pathway, ICWS acting probably at levels "downstream" from the opiate-sensitive site, while CCWS induces analgesia by acting on a different system which is not mediated by opioids.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Analgesia*
  • Animals
  • Cold Temperature*
  • Drug Tolerance
  • Male
  • Morphine / pharmacology*
  • Physical Exertion*
  • Rats
  • Rats, Inbred Strains
  • Stress, Physiological / physiopathology*
  • Swimming


  • Morphine