
OrphaninFQ(nociceptin,OFQ),aheptadecapeptidepeptide,hasbeendesignatedasanendogenousligandfortheORL1receptor.TheaminoacidsequenceofOFQhashomologywithotheropioidpeptides,especiallytheprodynorphinfragment dynorphinA,suggestingacloseevolutionaryrelationshipbetweentheprecursors.AdiffusedistributionthroughoutthebrainisseenwithbindingstudiesandinsituhybridizationsuggestinganextensiveroleforOFQinamultitudeofCNSfunctions.ImmunocytochemicallocalizationsinratspinalcordhavedemonstratedOFQabundanceinsuperficialdorsalhorn,lateralspinalnucleusandtheregiondorsaltothecentralcanal.OFQimmunoreactivitywasnotaffectedbydorsalrhizotomy,indicatingthatinspinalcordthepeptideisproducedbycentralratherthanprimaryafferentneurons.Thelocalizationissupportedbyitsfunctioninprocessingofnociceptivesignals.
Note:Peptidesequencecorrespondsto:aminoacids135-151ofrat,154-170ofmouseand130-146ofhumanpro-nociceptin.