title: Inability of naloxone to change brain morphine levels in tolerant mice.
abstract: The effect of naloxone on brain morphine concentrations was measured in naive and morphine-dependent mice using radioimmunoassay and gas-liquid chromatography. No displacement of morphine from the brain by naloxone could be observed in naive mice acutely injected with morphine or in pellet-implanted mice at increasing intervals after removal of the morphine pellets. The suggestion of a change in affinity of opiate receptors during the development of tolerance/dependence, which had been made on the basis of the displacement of morphine by naloxone found by other workers, is thus not supported by the present results.
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002849:Chromatography, Gas; D004361:Drug Tolerance; D051379:Mice; D009020:Morphine / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology*; D011863:Radioimmunoassay
chemical_list: D009270:Naloxone; D009020:Morphine