Cyclic somatostatin octapeptide analogues with high affinity and selectivity toward mu opioid receptors

Karoly Gulya, John T. Pelton, Victor J. Hruby, Henry I. Yamamura

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Abstract

A series of cyclic conformationally restricted penicillamine containing somatostatin octapeptide analogues have been prepared by standard solid phase synthetic techniques and tested for their ability to inhibit specific [125I]CGP 23,996 (des-Ala1-,Gly2-[desamino-Cys3Tyr11]-dicarba3,14- somatostatin), [3H]naloxone or [3H]DPDPE ([D-Pen2-D-Pen5]enkephalin) binding in rat brain membrane preparations. We now report structure-activity relationship studies with the syntheis of our most potent and selective mu opioid receptor compound DPheCysTyrDTrpOrnThrPenThrNH2, which we refer to as Cys2Tyr3Orn5Pen7-amide. While this octapeptide exhibited high affinity (IC50 = 2.80 nM) for an apparently single population of binding sites (nH = 0.89 ± 0.1) and exceptional selectivity for mu opioid receptos with an IC51(DPDPE)/IC50 (naloxone) ratio of 4,829, it also displayed very low affinity for somatostatin receptors (IC50 = 22,700 nM). Thus, Cys2Tyr3Orn5 Pen7-amide may be the ligand of choice for further characterization of mu opioid receptors and for examining the physiological role of this class of receptors.

Original languageEnglish (US)
Pages (from-to)2221-2229
Number of pages9
JournalLife Sciences
Volume38
Issue number24
DOIs
StatePublished - Jun 16 1986

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ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)

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