Title

A High Affinity, Highly Selective Ligand for the Delta Opioid Receptor: [3H]-[D-Pen2, pCl-Phe4, d-Pen5]enkephalin

Document Type

Article

Language

eng

Format of Original

8 p.

Publication Date

7-1989

Publisher

Elsevier

Source Publication

Life Sciences

Source ISSN

0024-3205

Original Item ID

doi: 10.1016/0024-3205(89)90154-9

Abstract

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.

Comments

Life Sciences, Vol. 45, No. 11 (July 1989): 1101-1108. DOI.