title: N-terminal modifications leading to peptide ORL1 partial agonists and antagonists.
abstract: Nociceptin/Orphanin FQ (N/OFQ) is a 17 amino acid peptide that is the endogenous ligand for the G protein-coupled receptor (opioid receptor like 1, ORL1), a member of the opioid receptor family. Although it is clear that this receptor system is involved in a variety of physiological functions, including analgesia, the precise actions of N/OFQ remain largely uncharacterized. One reason for this has been limited high affinity ligands to ORL1, and particularly the lack of availability of useful specific antagonists. Herein we describe the pharmacological activity of a series of N-terminally modified hexapeptides with high affinity for ORL1. These compounds were tested for binding affinity using [3H]N/OFQ binding to human ORL1 in CHO cells, and functional activity by measuring stimulation of [35S]GTPgammaS binding in CHO cell membranes. The N-terminal modifications have produced compounds that maintained very high receptor affinity, but led to significant changes in intrinsic activity. One compound, pentanoyl-RYYRWR-NH2, with barely measurable agonist activity was tested in vivo. It was found to possess modest analgesic activity, but it was unable to block the morphine modulatory activity of N/OFQ.
authors.affiliation: SynVax Inc., North Logan, UT 84341, USA. syntax@aol.com
authors.forename: A K
authors.initials: AK
authors.lastname: Judd
authors.forename: A
authors.initials: A
authors.lastname: Kaushanskaya
authors.forename: D J
authors.initials: DJ
authors.lastname: Tuttle
authors.forename: A
authors.initials: A
authors.lastname: Sanchez
authors.forename: T
authors.initials: T
authors.lastname: Khroyan
authors.forename: W
authors.initials: W
authors.lastname: Polgar
authors.forename: L
authors.initials: L
authors.lastname: Toll
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive; D016466:CHO Cells; D005576:Colforsin; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism*; D006801:Humans; D051379:Mice; D009292:Narcotic Antagonists / Q000494:pharmacology*; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology*; D018847:Opioid Peptides / Q000494:pharmacology; D010146:Pain / Q000188:drug therapy / Q000378:metabolism; D011957:Receptors, Opioid / Q000819:agonists* / Q000235:genetics; D013462:Sulfur Radioisotopes; D000094942:Nociceptin Receptor; D000097629:Nociceptin
chemical_list: D000701:Analgesics, Opioid; D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009292:Narcotic Antagonists; D009842:Oligopeptides; D018847:Opioid Peptides; D011957:Receptors, Opioid; D013462:Sulfur Radioisotopes; D000094942:Nociceptin Receptor; D000097629:Nociceptin