Abstract
A novel ligand for the nociceptin/orphanin FQ (N/OFQ) receptor (NOP), [(pF)Phe4,Arg14,Lys15]N/OFQ-NH2 (UFP-102), has been generated by combining in the N/OFQ-NH2 sequence two chemical modifications, [Arg14,Lys15] and [(pF)Phe4], that have been previously demonstrated to increase potency. In vitro, UFP-102 bound with high affinity to the human NOP receptor, showed at least 200-fold selectivity over classical opioid receptors, and mimicked N/OFQ effects in CHOhNOP cells, isolated tissues from various species, and mouse cortical synaptosomes releasing 5-hydroxytryptamine. UFP-102 showed similar maximal effects but higher potency (2- to 48-fold) relative to N/OFQ. The effects of UFP-102 were sensitive to NOP-selective antagonists J-113397 [(±)-trans-1-[1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one] (pA2 = 7.75–8.12) and UFP-101 ([Nphe1,Arg14,Lys15]N/OFQ-NH2)(pA2 = 6.91–7.33) but not to naloxone, and no longer observed in tissues taken from NOP receptor knockout mice (NOP–/–). In vivo, UFP-102 (0.01–0.3 nmol i.c.v.) mimicked the pronociceptive action of N/OFQ (0.1–10 nmol i.c.v.) in the mouse tail withdrawal assay, displaying higher potency and longer lasting effects. The action of UFP-102 was not apparent in NOP–/– mice. Similar results were obtained measuring locomotor activity in mice. In conscious rats, UFP-102 (0.05 nmol i.c.v.) produced a marked and sustained decrease in heart rate, mean arterial pressure, and urinary sodium excretion and a profound increase in urine flow rate. These effects were comparable with those evoked by N/OFQ at 5 nmol. Collectively, these findings demonstrate that UFP-102 behaves as a highly potent and selective NOP receptor agonist that produces long-lasting effects in vivo.
Footnotes
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This work was financially supported by the University of Ferrara (60% grant to G.C.), the Italian Ministry of the University (Grant FIRB 2001 to D.R.), by the International Association for the Study of Pain (collaborative travel grant Leicester/Ferrara), and by National Institutes of Health (collaborative Grant NHLBI HL-71212 to D.R.K. and D.R., and NIDDK DK-43337 and DK-02605 to D.R.K.).
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doi:10.1124/jpet.104.077339.
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ABBREVIATIONS: N/OFQ, nociceptin/orphanin FQ; NOP, nociceptin/orphanin FQ peptide receptor; J-113397, (±)-trans-1-[1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one; UFP-101, [Nphe1,Arg14,Lys15]N/OFQ-NH2; UFP-102, [(pF)Phe4,Arg14,Lys15]N/OFQ-NH2; 5-HT, 5-hydroxytryptamine; CHO, Chinese hamster ovary; KOP, κ-opioid peptide receptor; DOP, δ-opioid peptide receptor; MOP, μ-opioid peptide receptor; [35S]GTPσS, guanosine 5′-O-(3-[35S]thio)triphosphate; BSA, bovine serum albumin; ANOVA, analysis of variance; SB-612111, (–)-cis-1-methyl-7-[[4-(2,6-dichlorophenyl)piperidin-1-yl]methyl]-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol; Ro 64-6198, (1S,3aS)-8-(2,3,3a,4,5,6-hexahydro-1H-phenalen-1-yl)-1-phenyl-1,3,8-triaza-spiro[4.5]decan-4-one; ZP120, Ac-RYYRWK(7)-NH2.
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↵1 G.C. and A.R. contributed equally to this work.
- Received September 8, 2004.
- Accepted October 25, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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