Assessment of the activity of a novel nociceptin/orphanin FQ analogue at recombinant human nociceptin/orphanin FQ receptors expressed in Chinese hamster ovary cells.
The neuropeptide nociceptin/orphanin FQ (N/OFQ) is the endogenous ligand for the nociceptin receptor (NOP). In an attempt to identify high potency NOP agonists for use in the brain we have compared the activity of a novel N/OFQ analogue [Phe(1)Psi(CH(2)-O)Gly(2)]N/OFQ(1-13)NH(2) ([F/G-O]) with the existing [Phe(1)Psi(CH(2)-NH)Gly(2)]N/OFQ(1-13)NH(2) ([F/G]). Both peptides are modified between the first two N-terminal amino acids and are further compared with the agonist template N/OFQ(1-13)NH(2) in [(3)H]N/OFQ binding, GTPgamma[(35)S] binding and cAMP inhibition studies using Chinese hamster ovary cells expressing the recombinant human NOP. All peptides displaced [(3)H]N/OFQ, stimulated GTPgamma[(35)S] binding and inhibited cAMP formation. In [(3)H]N/OFQ binding and GTPgamma[(35)S] binding the rank order affinity and potency was N/OFQ(1-13)NH(2)>[F/G-O]>[F/G]. In GTPgamma[(35)S] binding [F/G] was a clear partial agonist with intrinsic activity (E(max) stimulation factor, mean+/-SEM, n=4) of 7.75+/-1.02 compared with N/OFQ(1-13)NH(2) of 11.13+/-1.76. The efficacy of [F/G-O] (10.17+/-1.88) approached that of the full agonist N/OFQ(1-13)NH(2). Downstream, at the level of cAMP formation, all peptides were full agonists with the following rank order potency: N/OFQ(1-13)NH(2)>[F/G-O]=[F/G]. The enhanced potency and intrinsic activity of the novel [F/G-O] modification makes this an interesting peptide for further in vivo analysis.
Wright
K E
KE
University Department of Anaesthesia, Critical Care and Pain Management, Leicester Royal Infirmary, LE1 5WW, Leicester, UK.
McDonald
J
J
Barnes
T A
TA
Rowbotham
D J
DJ
Guerrini
R
R
Calo'
G
G
Lambert
D G
DG
D000818:Animals; D001667:Binding, Competitive; D016466:CHO Cells; D006224:Cricetinae; D000242:Cyclic AMP / Q000096:biosynthesis; D006801:Humans; D018847:Opioid Peptides / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D011869:Radioligand Assay; D011957:Receptors, Opioid / Q000819:agonists* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D000094942:Nociceptin Receptor
D018847:Opioid Peptides; D010446:Peptide Fragments; D011957:Receptors, Opioid; D011994:Recombinant Proteins; C477498:nociceptin (1-13), Phe(1)psi(CH2-O)Gly(2); C114149:nociceptin (1-13)-NH2, Phe(1)-psi(CH2-NH)-Gly(2)-; D000242:Cyclic AMP; D000094942:Nociceptin Receptor