title: Study in vitro and in vivo of nociceptin/orphanin FQ(1-13)NH2 analogues substituting N-Me-Gly for Gly2 or Gly3.
abstract: In the present study, two analogues containing N-Me-Gly (Sarcosine, Sar) were synthesized to further investigate the structural-activity relationships of orphanin FQ/nociceptin (OFQ/NC, NC). The replacement of Gly(2) or Gly(3) with Sar increased the flexibility and decreased the hydrophobicity of the N-terminal tetrapeptide. The activity of the analogues was investigated in a series of assays in vivo and in vitro. [Sar(2)]NC(1-13)NH(2) was found to (1) produce dose-dependent inhibition of the electrically induced contraction in MVD assay (pEC(50) = 6.14); (2) produce significant hyperalgesia effects in a dose-dependent manner when intracerebroventricularly (i.c.v.) injected in mice. The inhibitive effects of [Sar(2)]NC(1-13)NH(2) in MVD assay could be significantly antagonized by [Nphe(1)]NC(1-13)NH(2), and partially antagonized by naloxone; the hyperalgesic effect of [Sar(2)]NC(1-13)NH(2) could be significantly antagonized by naloxone, and partially antagonized by [Nphe(1)]NC(1-13)NH(2). On the contrary, [Sar(3)]NC(1-13)NH(2) showed no effects in these assays. All the findings suggest that the flexibility of the peptide bond between Phe(1) and Gly(2) and between Gly(2) and Gly(3) play an important role in NC-OP(4) receptor interaction, and the hydrophobicity of the N-terminal tetrapeptide showed no significant effect on this interaction. The present work also helps to provide a novel method to elucidate structural and conformational requirements of the opioid peptide-receptor interaction.
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Life Science, Lanzhou University, 222 Tian Shui South Road, Lanzhou 730000, PR China.
authors.forename: Li-xiang
authors.initials: LX
authors.lastname: Chen
authors.forename: Quan
authors.initials: Q
authors.lastname: Fang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Chen
authors.forename: Jia
authors.initials: J
authors.lastname: Guo
authors.forename: Zhuan-zi
authors.initials: ZZ
authors.lastname: Wang
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D005998:Glycine / Q000737:chemistry; D008297:Male; D051379:Mice; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology*; D018847:Opioid Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D010147:Pain Measurement / Q000187:drug effects; D012521:Sarcosine / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014649:Vas Deferens / Q000187:drug effects; D000097629:Nociceptin
chemical_list: D005998:Glycine; D009842:Oligopeptides; D018847:Opioid Peptides; D012521:Sarcosine; D000097629:Nociceptin