Ac-RYYRWK-NH2 is a highly effective and specific partial agonist for the nociceptin receptor (NOP). It demonstrates a remarkable affinity for rat cortical membranes ORL1, with [3H]Ac-RYYRWK-NH2 exhibiting a Kd value of 0.071 nM. However, it shows negligible affinity towards μ-, κ-, or δ-opioid receptors.
Potent, selective partial agonist peptide for the NOP receptor (Ki = 0.71 nM). Selective over μ, δ and κ opioid receptors (IC50 > 4000 nM). Increases food intake in vivo.