Opioid receptor types and antinociceptive activity in chronic inflammation: both kappa- and mu-opiate agonistic effects are enhanced in arthritic rats

Eur J Pharmacol. 1986 Nov 4;130(3):203-8. doi: 10.1016/0014-2999(86)90269-4.


The antinociceptive effects obtained in arthritic rats with morphine, the opioid mu-agonist DAGO [D-Ala2,MePhe4,Gly-ol5]enkephalin, the delta-selective agonist DTLET [D-Thr2, Leu5]enkephalyl-Thr, and the kappa-agonist U-50,488H were compared to their corresponding effects in normal animals and morphine-pretreated arthritic rats, respectively, using a paw pressure test. The effects of the mu- and kappa-agonists were increased in arthritic rats. While morphine-treated rats were cross-tolerant to the mu- and kappa-agonists, no tolerance to the delta-selective agonist was found. The possibility that the potent action of morphine in this model for chronic inflammatory pain is mediated partly through kappa-mechanisms is discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics*
  • Animals
  • Arthritis / metabolism*
  • Arthritis, Experimental / metabolism*
  • Body Weight / drug effects
  • Chronic Disease
  • Endorphins / pharmacology
  • Male
  • Morphine / pharmacology
  • Rats
  • Rats, Inbred Strains
  • Receptors, Opioid / drug effects*
  • Receptors, Opioid / physiology
  • Receptors, Opioid, kappa
  • Receptors, Opioid, mu


  • Analgesics
  • Endorphins
  • Receptors, Opioid
  • Receptors, Opioid, kappa
  • Receptors, Opioid, mu
  • Morphine