Nociceptin / Orphanin FQ
Overview
Nociceptin, also known as orphanin FQ, is a 17-amino acid peptide that acts as the endogenous ligand for the nociceptin/orphanin FQ peptide (NOP) receptor, a member of the opioid receptor family with distinct pharmacology. Despite structural similarity to dynorphin A, nociceptin does not bind classical opioid receptors. Its effects on pain are complex and context-dependent, producing analgesia at the spinal level but pronociceptive or hyperalgesic effects at supraspinal sites. The peptide also modulates stress, anxiety, and reward pathways.
Key Research Findings
Preclinical research has extensively characterized nociceptin's bidirectional effects on pain processing across different anatomical sites and pain models. Clinical development has focused on small-molecule NOP receptor agonists and mixed NOP/mu-opioid ligands rather than the native peptide. Phase 2 trials of cebranopadol, a dual NOP/mu agonist, have shown analgesic efficacy in chronic pain, though nociceptin itself remains a research tool.
Endogenous peptide
Research Phase
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