A high affinity, highly selective ligand for the delta opioid receptor: [3H]-[D-PEN2, pCl-PHE4, D-PEN5]enkephalin

Linda K. Vaughn, Richard J. Knapp, Geza Toth, Y. P. Wan, Victor J. Hruby, Henry I. Yamamura

Research output: Contribution to journalArticlepeer-review

90 Scopus citations


Binding characteristics of a new, conformationally constrained, halogenated enkephalin analogue, [3H]-[D-penicillamine2, pCl-Phe4, D-penicillamine5]enkephalin ([3H]pCl-DPDPE), were determined using homogenized rat brain tissue. Saturation binding studies at 25°C determined a dissociation constant (Kd) of 328 ± 27 pM and a receptor density (Bmax) of 87.2 ± 4.2 fmol/mg protein. Kinetic studies demonstrated biphasic association for [3H]pCl-DPDPE, with association rate constants of 5.05 × 108 ± 2.5 × 108 and 0.147 ± 108 ± 0.014 × 108 M-1 min-1. Dissociation was monophasic with a dissociation rate constant of 2.96 × 10-3 ± 0.25 × 10-1 min-1. The average Kd values determined by these kinetic studies were 8.4 ± 2.7 pM and 201 ± 4 pM. Competitive inhibition studies demonstrated that [3H]pCl-DPDPE has excellent selectively for the delta opioid receptor. [3H]pCl-DPDPE binding was inhibited by low concentrations of ligands selective for delta opioid receptor relative to the concentrations required by ligands selective for mu and kappa sites. These data show that [3H]pCl-DPDPE is a highly selective, high affinity ligand which should be useful in characterizing the delta opioid receptor.

Original languageEnglish (US)
Pages (from-to)1001-1008
Number of pages8
JournalLife Sciences
Issue number11
StatePublished - 1989

ASJC Scopus subject areas

  • General Pharmacology, Toxicology and Pharmaceutics
  • General Biochemistry, Genetics and Molecular Biology


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