Morphine-induced downregulation of μ-opioid receptors in neonatal rat brain

Ann Tempel, Jo Ellen Habas, William Paredes, Gordon A. Barr

Research output: Contribution to journalArticlepeer-review

92 Scopus citations


Chronic administration of morphine to pre- and postnatal rats produced a marked decrease in brain μ-opioid receptor density without a change in receptor affinity. No significant changes in δ- or κ-receptors were observed. This downregulation was accompanied by tolerance to the analgesic actions of morphine. In neonates exposed to morphine from postnatal day one, μ-receptor number was significantly depressed until postnatal day 8, then increased gradually to control levels by day 14 of treatment. Longer treatment produced no further change in opioid receptors. These data represent the first demonstration of in vivo downregulation of brain μ-opioid receptors following morphine administration and provide evidence for a unique plasticity of the immature opioid receptor system.

Original languageEnglish (US)
Pages (from-to)129-133
Number of pages5
JournalDevelopmental Brain Research
Issue number1-2
StatePublished - Jun 1 1988


  • Brain opioid receptor development
  • Brain μ-receptor
  • Chronic agonist
  • Downregulation
  • Morphine
  • Neonate
  • Tolerance

ASJC Scopus subject areas

  • Developmental Neuroscience
  • Developmental Biology


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