Nociceptin/orphanin FQ (N/OFQ) is a 17-amino acid neuropeptide and an endogenous ligand for the nociceptin receptor (NOP, ORL-1). Nociceptin is derived from the prepronociceptin protein, as also are nocistatin and NocII, which inhibit N/OFQ receptor function. The name €~nociceptin€(TM) derives from the discovery that it can produce a pro-nociceptive response, and nociceptin acts as an anti-analgesic, counteracting the effect of pain-relievers. Nociceptin is widely distributed in the CNS and acts on numerous brain activities including pain sensation and fear. When administered to the spinal cord, nociceptin produces similar analgesic effects to the classical opioids.
