Antinociception mediated by the periaqueductal gray is attenuated by orphanin FQ

Michael M. Morgan, Judith E. Grisel, Carolyn S. Robbins, David K. Grandy

Research output: Contribution to journalArticlepeer-review

105 Scopus citations


Orphanin FQ or nociceptin (OFQ/N1-17) is a recently discovered peptide which, upon intracerebroventricular administration, reverses opioid- mediated analgesias. OFQ/N1-17 terminals are located in the periaqueductal gray (PAG), a structure known to be involved in pain modulation, suggesting that the functional anti-opioid effects of OFQ/N1- 17 are mediated by PAG neurons. To test this, subsequent microinjections of morphine or kainic acid and OFQ/N1-17 were made into the PAG of awake rats. Administration of OFQ/N1-17 attenuated the tail flick inhibition produced by both morphine and kainic acid microinjection. OFQ/N1-17 attenuation of antinociception produced by a neuroexcitant indicates that OFQ/N1-17 reverses opioid antinociception by inhibiting PAG output neurons.

Original languageEnglish (US)
Pages (from-to)3431-3434
Number of pages4
Issue number16
StatePublished - 1997
Externally publishedYes


  • Analgesia
  • Anti-opioid peptide
  • Morphine
  • Nociceptin
  • Opioid
  • Pain modulation

ASJC Scopus subject areas

  • General Neuroscience


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