Both [d-Ala2, Glu4]Deltorphin and [d-Ala2, 4′-I-Phe3, Glu4]Deltorphin are highly selective ligands for δ, relative to μ, opioid receptors. Radiolabeled [d-Ala2, 4′-125I-Phe3, Glu4]Deltorphin ([125I]Deltorphin) was prepared with a specific activity of 2200 Ci/mmol from [d-Ala2, 4′-NH2-Phe3, Glu4]Deltorphin through a diazonium salt intermediate. The inhibition of [125I]Deltorphin binding to rat brain membranes by ligands selective for μ, δ, and κ opioid receptors is consistent with binding by the radioligand to a single site having the properties of a δ opioid receptor. The results of these studies are in good agreement with those obtained by structurally different δ opioid receptor ligands. The similarity between the δ receptor site labeled by [125I]Deltorphin and those labeled by other δ receptor agonists, in contrast to differences seen by in vivo studies of their analgesic effects, is discussed.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)