Bidirectional modulatory effect of orphanin FQ on morphine-induced analgesia: Antagonism in brain and potentiation in spinal cord of the rat

Jin Hua Tian, Wei Xu, Yuan Fang, Jeffrey S. Mogil, Judith E. Grisel, David K. Grandy, Ji Sheng Han

Research output: Contribution to journalArticlepeer-review

230 Scopus citations

Abstract

1. The present study was designed to investigate further the effects of the newly discovered orphanin FQ (OFQ) - the endogenous ligand for the orphan opioid receptor (called, e.g., ORL1 and LC132) - on pain modulation in the rat. We used the tail-flick assay as a nociceptive index. 2. When injected into a cerebral ventricle, OFQ (4 fmol-10 nmol) has no effect on basal tail-flick latency by itself at any dose, but dose-dependently antagonizes systemic morphine analgesia (400 fmol-50 nmol). 3. Injected intrathecally, OFQ (3 and 10 nmol) displayed an analgesic effect without producing motor dysfunction, and potentiated morphine analgesia (1 and 10 nmol). 4. The anti-opioid effect of OFQ in rat brain and the high level of expression of LC132/ORL1 receptor in the locus coeruleus indicated a possible role of OFQ in the precipitation of opiate withdrawal symptoms. However, no such precipitation was observed by OFQ in morphine-dependent rats.

Original languageEnglish (US)
Pages (from-to)676-680
Number of pages5
JournalBritish Journal of Pharmacology
Volume120
Issue number4
DOIs
StatePublished - 1997
Externally publishedYes

Keywords

  • Analgesia
  • Anti-opioid
  • Morphine withdrawal
  • ORL/LC132
  • Orphanin FQ/nociceptin

ASJC Scopus subject areas

  • Pharmacology

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