title: Dependence in the absence of tolerance to morphine.
abstract: Intravenous morphine depressed the firing of cat dorsal horn neurones to impulses in unmyelinated primary afferents. Electrophoretic administration of naloxone in the substantia gelatinosa between 10 min and 6 h after morphine revealed hyper-responsiveness which was not associated with apparent tolerance to morphine. The observations suggest the changes underlying dependence occur very rapidly in the dorsal horn probably at a site different from that at which morphine acts.
mesh_terms: D000200:Action Potentials; D000818:Animals; D002415:Cats; D004361:Drug Tolerance; D004558:Electric Stimulation; D006801:Humans; D009020:Morphine; D009474:Neurons / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology*; D019966:Substance-Related Disorders; D013376:Substantia Gelatinosa / Q000502:physiology*
chemical_list: D009020:Morphine