Chronic antagonist infusion does not increase morphine antinociception in rat spinal cord

Craig W. Stevens, Tony L. Yaksh

Research output: Contribution to journalArticle

4 Scopus citations


Chronic spinal infusion of the opiate antagonist naloxone or naltrexone fail to influence the antinociceptive effect of subsequent intrathecal morphine on the hot plate test in rats compared to saline-infused controls. These results contrast the functional supersensitivity to morphine seen after long-term systemic opiate antagonist administration and support the hypothesis that dopaminergic interactions, lacking in the spinal cord, are necessary for antagonist-induced opioid receptor upregulation.

Original languageEnglish
Pages (from-to)388-390
Number of pages3
JournalBrain Research
Issue number2
Publication statusPublished - 10 Nov 1987



  • Antinociception
  • Morphine
  • Naloxone
  • Naltrexone
  • Opioid receptor
  • Upregulation

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