Morphine analgesia and acute physical dependence: rapid onset of two opposing, dose-related processes

Dong H. Kim, Howard L. Fields, Nicholas M. Barbaro

Research output: Contribution to journalArticle

65 Scopus citations


Enhanced responsiveness to noxious stimulation is a reliable sign of opioid withdrawal and is therefore a measure of physical dependence. In lightly anesthetized rats, naloxone, given i.v. 15 min following i.v. morphine, caused a significant shortening of tail flick latency (hyperalgesia). At each dose of naloxone (0.1, 1.0 or 2.0 mg/kg), the magnitude of the observed hyperalgesia was a function of the preceding dose of morphine (0.5, 1.0 or 2.0 mg/kg). Thus morphine rapidly induces two dose-related opposing processes: one results in antinociception and the other in the potential for hyperalgesia.

Original languageEnglish (US)
Pages (from-to)37-40
Number of pages4
JournalBrain research
Issue number1
StatePublished - May 14 1990



  • Analgesia
  • Dependency
  • Morphine
  • Opioid withdrawal

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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