Endogenous opioids may mediate the centrally-induced gastroprotective action of nociceptin and nocistatin

Background: Nociceptin/Orphanin FQ (Noc) and Nocistatin (NS) are two neuropeptides derived from the same precursor protein, pre-pro-Nociceptin (Okuda-Ashitaka and Seiji, 2000). Noc is considered to be the endogenous ligand of the NOP receptor, which exhibits marked structural analogy with the other classic opioid receptors. However, Noc lacks the N-terminal tyrosine necessary for the activation of the opioid receptors, and its effects are usually not reversed by naloxone. Central and peripheral administration of the Noc has been reported to exert multiple effects in the gastrointestinal (GI) tract, for example i…