Microdialysis reveals a morphine-induced increase in pallidal opioid peptide release

M. Foster Olive, Magali Bertolucci, Christopher J. Evans, Nigel T. Maidment

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Freely moving rats were implanted with microdialysis probes in the globus pallidus/ventral pallidum, nucleus accumbens or caudate nucleus. Morphine (10 mg kg−1 i.p.) induced an average 128% increase in extracellular opioid peptide levels in the pallidum over a 2 h period peaking 1 h after injection. No change was observed in the nucleus accumbens or caudate nucleus. Dose-response analysis showed a smaller (26%), non-significant, increase at a lower dose of 2 mg kg−1 and no effect at a higher dose of 40 mg kg−1. No evidence of significant acute tolerance was apparent following repeated administration of morphine (10 mg kg−1, i.p.) at 3 h intervals. The magnitude of the morphine effect varied greatly between animals and was dependent on the pre-injection baseline opioid peptide levels.

Original languageEnglish (US)
Pages (from-to)1093-1096
Number of pages4
Issue number8
StatePublished - May 1995
Externally publishedYes


  • Drug abuse
  • Enkephalin
  • Microdialysis
  • Morphine
  • Opiate
  • Opioid peptide
  • Pallidum
  • Release
  • Reward

ASJC Scopus subject areas

  • Neuroscience(all)


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