Cross-tolerance and convergent dependence between morphine and cannabimimetic agent WIN 55,212-2 in the guinea-pig ileum myenteric plexus

Eur J Pharmacol. 1999 Jul 9;376(3):265-71. doi: 10.1016/s0014-2999(99)00389-1.


The cross-tolerance and convergent dependence between morphine and the cannabimimetic agent R(+)-[2,3-dihydro-5-methyl-3[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-+ ++benzoxazin-yl]-(1-naphthalenyl) methanone mesylate (WIN 55,212-2) were assessed in vitro on guinea-pig ileum. To induce tolerance and dependence the myenteric plexus-longitudinal muscle was incubated at 37 degrees C for 5 h with a fixed concentration representing the IC50 for each compound. Myenteric plexus-longitudinal muscle exposed to WIN 55,212-2 (5 x 10(-8) M) was less sensitive to its inhibitory effect on electrically evoked contractions than naive myenteric plexus-longitudinal muscle. The exposure to cannabinoid induced a parallel rightward shift in the lower part of the concentration-response curve of WIN 55,212-2 and a marked reduction in the maximal inhibitory effect of the drug. Myenteric plexus-longitudinal muscle tolerant to WIN 55,212-2 was subsensitive to the inhibitory effect of morphine on the twitch response. The cross-tolerance between WIN 55,212-2 and morphine was bidirectional. In fact, after 5 h the morphine (10(-7) M)-incubated myenteric plexus-longitudinal muscle was less sensitive to the inhibitory effect of WIN 55,212-2. The tissue tolerant to morphine or WIN 55,212-2 was tested for the presence of physical dependence. Naloxone (10(-5) M) produced a typical withdrawal contracture in morphine-tolerant myenteric plexus-longitudinal muscle which could be reduced by a 15-min pretreatment with WIN 55,212-2 (5 X 10(-8) M). In contrast, SR141716 (10(-6) M) [N-(piperidino)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyr azole-carboxamide], a concentration which fully antagonized the inhibitory effect of WIN 55,212-2 (10(-7) M) in control preparations, did not produce significant contracture in WIN 55,212-2-tolerant myenteric plexus-longitudinal muscle. The mechanisms underlying the cross-tolerance and convergent dependence remain to be ascertained.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics, Opioid / pharmacology*
  • Animals
  • Benzoxazines
  • Cannabinoids / pharmacology*
  • Dose-Response Relationship, Drug
  • Drug Resistance
  • Drug Tolerance
  • Female
  • Guinea Pigs
  • Ileum / drug effects
  • Morphine / pharmacology*
  • Morpholines / pharmacology*
  • Muscle Contraction / drug effects
  • Myenteric Plexus / drug effects*
  • Naphthalenes / pharmacology*


  • Analgesics, Opioid
  • Benzoxazines
  • Cannabinoids
  • Morpholines
  • Naphthalenes
  • (3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone
  • Morphine