title: Reinitiation of sensitivity to naloxone by a single narcotic injection in postaddicted mice.
abstract: In mice implanted with a morphine pellet for 3 days and subsequently withdrawn for various periods of time, a single injection of morphine results in a rapid and marked sensitization of abstinent mice to naloxone-induced jumping behavior when compared to abstinent mice pretreated with saline or to placebo-withdrawn mice given a single morphine injection. Maximum sensitization of abstinent mice occurs at morphine doses of about 10 to 30 mg/kg and peaks at 0.5 to 2 hours after morphine administration. The ability of morphine to sensitize abstinent mice to naloxone declines with time after pellet removal and appears to consist of two components, one with a short T1/2 and one with a much longer T1/2. Abstinent mice are also sensitized to naloxone by levorphanol and methadone, but not by dextrorphan. It is proposed that the administration of a narcotic drug to abstinent mice uncovers a latent, pre-existing state of physical dependence and restores the responsiveness of this state to naloxone.
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D003429:Cross Reactions; D004347:Drug Interactions; D006801:Humans; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009021:Morphine Dependence / Q000503:physiopathology*; D009270:Naloxone / Q000032:analysis / Q000494:pharmacology*; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology; D013997:Time Factors
chemical_list: D009270:Naloxone; D009020:Morphine