Role of the kappa-opioid system in the attenuation of the morphine-induced place preference under chronic pain.

Abstract

We previously reported that the morphine-induced place preference was attenuated under inflammation produced by the unilateral injection of 2.5 % formalin (50 microl) into the hind paw of rats. In the present study, to elucidate the mechanism of this attenuation, the effects of pretreatment with delta- and kappa-opioid receptor antagonists, naltrindole (NTI) and nor-binaltorphimine (nor-BNI), on the development of the morphine-induced place preference under inflammation were examined in rats. Nor-BNI, but not NTI, eliminated the suppression of the morphine-induced place preference in inflamed groups. These results suggest that endogenous kappa-opioid systems may be activated in the presence of chronic inflammatory nociception; as a result, the development of morphine's rewarding effect may be suppressed under inflammation.

• Authors: T Suzuki, Y Kishimoto, M Misawa, H Nagase, F Takeda
• Journal: Life sciences (Life Sci) Vol. 64 Issue 1 Pg. PL1-7 ( 1999) ISSN: 0024-3205 [Print] Netherlands
• PMID: 10027746 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Receptors, Opioid, delta
• Receptors, Opioid, kappa
• Formaldehyde
• norbinaltorphimine
• Naltrexone
• Morphine
• naltrindole

Topics

• Animals
• Chronic Disease
• Conditioning, Psychological (drug effects)
• Formaldehyde (pharmacology)
• Hindlimb
• Inflammation (chemically induced, physiopathology)
• Male
• Morphine (pharmacology)
• Naltrexone (analogs & derivatives, pharmacology)
• Pain (drug therapy, physiopathology)
• Rats
• Rats, Sprague-Dawley
• Receptors, Opioid, delta (antagonists & inhibitors, physiology)
• Receptors, Opioid, kappa (antagonists & inhibitors, physiology)
• Reward
• Time Factors