Nociceptin
[Arg14,Lys15]Nociceptin is a highly potent and selective NOP receptor (ORL1; OP4) agonist, with an EC50 of 1 nM. [Arg14,Lys15]Nociceptin displays high selectivity over opioid receptors, with IC50s of 0.32, 280, >10000 and 1500 nM for NOP, μ, δ and κ receptors, respectively.