- G Carra': Section of Pharmacology and Neuroscience Centre, Department of Experimental and Clinical Medicine, University of Ferrara, 44100 Ferrara, Italy.
In the present study we describe the in vitro pharmacological characterization of the nociceptin/orphanin FQ (N/OFQ) receptor (NOP) ligand Ac-RYYRWK-NH2 and the synthesis and biological evaluation of 13 Trp5 substituted Ac-RYYRWK-NH2 analogs. Results indicate that Ac-RYYRWK-NH2 behaves as a highly potent and selective partial agonist at the NOP receptors and that the whole indole moiety of the Trp5 side chain is not required, being a phenyl-ethyl side chain already sufficient for maintaining high potency.