PRESENCE AND CHARACTERIZATION OF NOCICEPTIN (ORPHANIN FQ) RECEPTOR-BINDING IN ADULT-RAT AND HUMAN FETAL HYPOTHALAMUS

High affinity and saturable nociceptin (orphanin FQ) receptors were de tected and characterized in adult rat and human fetal hypothalamic mem branes, utilizing [I-125]Tyr(12)-nociceptin as ligand. Nociceptin boun d with picomolar affinity, dynorphin A with nanomolar affinity, naloxo ne and dynorphan A(1-8) with micromolar while des-Tyr(1)-dynorphin (dy norphin A(2-17)), several other opioids, morphine and benzomorphans fa iled to compete for binding at 1-10 mu M. Gpp(NH)p together with sodiu m ion markedly decreased binding, consistent with involvement of a G p rotein-linked receptor. (C) 1997 Elsevier Science B.V.