Relationship between binding affinity and functional activity of nociceptin/orphanin FQ.
The relationship between binding affinity and functional activity of nociceptin/orphanin FQ binding was studied in brain membranes, membranes of Chinese hamster ovary cells transfected with ORL1, and intact CHO-ORL1 cells. Binding affinities were compared with potency for the stimulation of [35S]GTP gamma S binding in cell membranes, and inhibition of forskolin-stimulated cAMP accumulation in intact cells. Binding was conducted with [3H]14-Tyr-nociceptin, and in brain or cell membranes the affinity was found to be 50-100 pM. The binding of [3H]14-Tyr-nociceptin was found to be regulated by Na+ and GTP, as expected for an opioid-like receptor. In intact cells, saturation produced a curvilinear Scatchard Plot. Non-linear analysis indicated two states of the receptor, with the vast majority of binding being to a low affinity state of approximately 8 nM. This low affinity component is consistent with the lower potency derived from the inhibition of cAMP accumulation, stimulation of [35S]GTP gamma S binding, and other functional assays.
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Department of Neuroscience, SRI International, Menlo Park, CA 94025, USA.
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D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D016466:CHO Cells; D006224:Cricetinae; D006168:Guinea Pigs; D016015:Logistic Models; D018847:Opioid Peptides / Q000378:metabolism / Q000502:physiology*; D011957:Receptors, Opioid / Q000819:agonists*; D000097629:Nociceptin
D018847:Opioid Peptides; D011957:Receptors, Opioid; D000097629:Nociceptin