Orphanin FQ: A neuropeptide that activates an opioidlike G protein-coupled receptor

Rainer K. Reinscheid, Hans Peter Nothacker, Anne Bourson, Ali Ardati, Robert A. Henningsen, James R. Bunzow, David K. Grandy, Hanno Langen, Frederick J. Monsma, Olivier Civelli

Research output: Contribution to journalArticlepeer-review

1764 Scopus citations


A heptadecapeptide was identified and purified from porcine brain tissue as a ligand for an orphan heterotrimeric GTP- binding protein (G protein)- coupled receptor (LC132) that is similar in sequence to opioid receptors. This peptide, orphanin FQ, has a primary structure reminiscent of that of opioid peptides. Nanomolar concentrations of orphanin FQ inhibited forskolin-stimulated adenylyl cyclase activity in cells transfected with LC132. This inhibitory activity was not affected by the addition of opioid ligands, nor did the peptide activate opioid receptors. Orphanin FQ bound to its receptor in a saturable manner and with high affinity. When injected intracerebroventricularly into mice, orphanin FQ caused a decrease in locomotor activity but did not induce analgesia in the hot-plate test. However, the peptide produced hyperalgesia in the tail-flick assay. Thus, orphanin FQ may act as a transmitter in the brain by modulating nociceptive and locomotor behavior.

Original languageEnglish (US)
Pages (from-to)792-794
Number of pages3
Issue number5237
StatePublished - 1995
Externally publishedYes

ASJC Scopus subject areas

  • General


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