Biochemical evidence for orphanin FQ/nociceptin receptor heterogeneity in mouse brain.
A recently identified novel peptide, orphanin FQ/nociceptin (OFQ/N), is an endogenous ligand for a unique member of the cloned opioid receptor family. Saturation studies in mouse brain membranes reveal curvilinear Scatchard plots with both a higher (KD 3.8 pM, Bmax 31.6 fmol/mg protein) and a lower (KD 896 pM, Bmax 233 fmol/mg protein) affinity site in brain tissue, compared to only a single site in transfected CHO cells (KD 36 pM). Competition studies confirm the high affinity of OFQ/N for this site, but shallow Hill slopes suggest heterogeneity. Traditional opioids have poor affinity for this receptor and OFQ/N and its fragments do not label traditional opioid receptors. In brain homogenates, both OFQ/N and OFQ/N(1-11) inhibit forskolin-stimulated camp accumulation with IC50 values of 1 nM or less, an action which is readily reversed by opioid antagonists. OFQ/N(1-7) shows little activity. Together, these studies suggest the presence of heterogeneous, functionally active OFQ/N receptors in mouse brain.
Mathis
J P
JP
The George C. Cotzias Laboratory of Neuro-Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Ryan-Moro
J
J
Chang
A
A
Hom
J S
JS
Scheinberg
D A
DA
Pasternak
G W
GW
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D004399:Dynorphins / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D009294:Narcotics / Q000494:pharmacology; D018847:Opioid Peptides / Q000378:metabolism* / Q000494:pharmacology; D011869:Radioligand Assay; D011957:Receptors, Opioid / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D000094942:Nociceptin Receptor; D000097629:Nociceptin
D004399:Dynorphins; D004745:Enkephalins; D009294:Narcotics; D018847:Opioid Peptides; D011957:Receptors, Opioid; D011994:Recombinant Proteins; D000094942:Nociceptin Receptor; D000097629:Nociceptin