title: A comprehensive study on the putative δ-opioid receptor (sub)types using the highly selective δ-antagonist, Tyr-Tic-(2S,3R)-β-MePhe-Phe-OH.
abstract: The goal of our work was a throughout characterization of the pharmacology of the TIPP-analog, Tyr-Tic-(2S,3R)-β-MePhe-Phe-OH and see if putative δ-opioid receptor subtypes can be distinguished. Analgesic latencies were assessed in mouse tail-flick assays after intrathecal administration. In vitro receptor autoradiography, binding and ligand-stimulated [(35)S]GTPγS functional assays were performed in the presence of putative δ(1)-(DPDPE: agonist, BNTX: antagonist), δ(2)-(agonist: deltorphin II, Ile(5,6)-deltorphin II, antagonist: naltriben) and μ-(DAMGO: agonist) opioid ligands. The examined antagonist inhibited the effect of DPDPE by 60%, but did not antagonize δ(2)- and μ-agonist induced analgesia. The radiolabeled form identified binding sites with K(D)=0.18 nM and receptor densities of 102.7 fmol/mg protein in mouse brain membranes. The binding site distribution of the [(3)H]Tyr-Tic-(2S,3R)-β-MePhe-Phe-OH agreed well with that of [(3)H]Ile(5,6)-deltorphin II as revealed by receptor autoradiography. Tyr-Tic-(2S,3R)-β-MePhe-Phe-OH displayed 2.49±0.06 and 0.30±0.01 nM potency against DPDPE and deltorphin II in the [(35)S]GTPγS functional assay, respectively. The rank order of potency of putative δ(1)- and δ(2)-antagonists against DPDPE and deltorphin was similar in brain and CHO cells expressing human δ-opioid receptors. Deletion of the DOR-1 gene resulted in no residual binding of the radioligand and no significant DPDPE effect on G-protein activation. Tyr-Tic-(2S,3R)-β-MePhe-Phe-OH is a highly potent and δ-opioid specific antagonist both in vivo and in vitro. However, the putative δ(1)- and δ(2)-opioid receptors could not be unequivocally distinguished in vitro.
authors.affiliation: Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, Szeged, P.O. Box 521, Hungary.
authors.forename: Erika
authors.initials: E
authors.lastname: Birkas
authors.forename: Lidia
authors.initials: L
authors.lastname: Bakota
authors.forename: Karoly
authors.initials: K
authors.lastname: Gulya
authors.forename: Ting
authors.initials: T
authors.lastname: Wen
authors.forename: John
authors.initials: J
authors.lastname: Pintar
authors.forename: Geza
authors.initials: G
authors.lastname: Tóth
authors.forename: Maria
authors.initials: M
authors.lastname: Szucs
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001345:Autoradiography; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D051379:Mice; D008810:Mice, Inbred C57BL; D009842:Oligopeptides / Q000737:chemistry / Q000494:pharmacology*; D017465:Receptors, Opioid, delta / Q000037:antagonists & inhibitors* / Q000145:classification; D044005:Tetrahydroisoquinolines / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000701:Analgesics, Opioid; D009842:Oligopeptides; D017465:Receptors, Opioid, delta; D044005:Tetrahydroisoquinolines; C082263:tyrosyl-1,2,3,4-tetrahydro-3-isoquinolinecarbonyl-phenylalanyl-phenylalanine