Analgesic and aversive effects of naloxone in BALB/c mice.
Opioid antagonists have been shown to produce dose-dependent analgesia in the formalin test in BALB/c mice. In light of this paradoxical finding, the motivational-affective property of naloxone was examined in BALB/c mice. Naloxone produced a conditioned place aversion at doses which were also found to produce analgesia in the formalin test (1 and 10 mg/kg). In addition, the analgesia produced by 1 mg/kg naloxone was completely abolished in mice pretreated with nor-binaltorphimine, a highly selective kappa-opioid antagonist. Norbinaltorphimine on its own, however, had no effect. These results suggest that the analgesic actions of naloxone may be due to an interaction with kappa receptors.
Vaccarino
A L
AL
Department of Psychology, University of New Orleans, Lakefront, Louisiana 70148.
Plamondon
H
H
Melzack
R
R
D000698:Analgesia; D000818:Animals; D002755:Choice Behavior / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005557:Formaldehyde; D051379:Mice; D008807:Mice, Inbred BALB C; D009270:Naloxone / Q000494:pharmacology*; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*
D005557:Formaldehyde; D009270:Naloxone; C051844:norbinaltorphimine; D009271:Naltrexone