In vitro functional characterization of novel nociceptin/orphanin FQ receptor agonists in recombinant and native preparations

Eur J Pharmacol. 2016 Dec 15;793:1-13. doi: 10.1016/j.ejphar.2016.10.025. Epub 2016 Oct 22.


Nociceptin/Orphanin FQ (N/OFQ) regulates several biological functions via selective activation of the N/OFQ receptor (NOP). In this study novel nonpeptide NOP ligands were characterized in vitro in receptor binding and [35S]GTPγS stimulated binding in membranes of cells expressing human NOP and classical opioid receptors, calcium mobilization assay in cells coexpressing the receptors and chimeric G proteins, bioluminescence resonance energy transfer (BRET) based assay for studying NOP receptor interaction with G protein and arrestin, the electrically stimulated mouse vas deferens and the mouse colon bioassays. The action of the AT compounds were compared with standard NOP agonists (N/OFQ and Ro 65-6570) and the NOP selective antagonist SB-612111. AT compounds displayed high NOP affinity and behaved as NOP agonists in all the functional assays consistently showing the following rank order of potency AT-127≥AT-090≥AT-035>AT-004= AT-001. AT compounds behaved as NOP full agonists in the calcium mobilization and mouse colon assays and as partial agonists in the [35S]GTPγS and BRET assays. Interestingly AT-090 and AT-127, contrary to standard nonpeptide agonists that display G protein biased agonism, behaved as an unbiased agonists. AT-090 and AT-127 displayed higher NOP selectivity than Ro 65-6570 at native mouse receptors. AT-090 and AT-127 might be useful pharmacological tools for investigating the therapeutic potential of NOP partial agonists.

Keywords: Bioluminescence resonance energy transfer; Calcium mobilization and mouse colon vas deferens and assays; NOP and classical opioid receptors; Receptor and [(35)S]GTPγS binding.

MeSH terms

  • Animals
  • CHO Cells
  • Colon / drug effects
  • Colon / metabolism
  • Cricetinae
  • Cricetulus
  • Cycloheptanes / metabolism
  • Cycloheptanes / pharmacology*
  • HEK293 Cells
  • Humans
  • Ligands
  • Male
  • Mice
  • Nociceptin Receptor
  • Piperidines / metabolism
  • Piperidines / pharmacology*
  • Receptors, Opioid / agonists*
  • Receptors, Opioid / genetics
  • Receptors, Opioid / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism*
  • Vas Deferens / drug effects
  • Vas Deferens / metabolism


  • Cycloheptanes
  • Ligands
  • Piperidines
  • Receptors, Opioid
  • Recombinant Proteins
  • cis-1-methyl-7-((4-(2,6-dichlorophenyl)piperidin-1-yl)methyl)-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol
  • Nociceptin Receptor