Nociceptin/Orphanin FQ

Nociceptin (N) and orphanin FQ (OFQ) are alternative names for a peptide discovered as an endogenous ligand for an orphan GPCR, originally named opioid receptor-like 1 (ORL-1). At present, the combined term N/OFQ is used for the peptide, and N/OFQ peptide receptor (NOP) for the receptor. The heptadecapeptide N/OFQ is generated from the precursor prepronociceptin by posttranslational proteolytic cleavage, and elicits hyperalgesia. N/OFQ selectively binds to NOP rather than to the classical opioid receptors (δ-opioid receptor, κ-opioid receptor, or μ-opioid receptor). N/OFQ is associated with a variety of biological processes, including locomotion, feeding, anxiety, spatial attention/learning, endocrine effects in the hypothalamus, reward, and opiate tolerance and dependence.