[3H]Naltrindole binding characteristics were determined using homogenized rat brain tissue. Saturation binding studies at 25°C measured an equilibrium dissociation constant (Kd) value of 37.0 ± 3.0 pM and a receptor density (Bmax) value of 63.4 ± 2.0 fmol/mg protein. Association binding studies showed that equilibrium was reached within 90 min at a radioligand concentration of 30 pM. Naltrindole, as well as the ligands selective for delta (δ) opioid receptors, such as pCI-DPDPE and Deltorphin II inhibited [3H]naltrindole binding with nanomolar IC50 values. Ligands selective for mu (μ) and kappa (κ) opioid receptors were only effective inhibiting [3H]naltrindole binding at micromolar concentrations. From these data, we conclude that [3H]naltrindole is a high affinity, selective radioligand for delta opioid receptors.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)