Displacement of opioid receptor binding ligands from the rat brain by N3-(2',5'-dimethoxyphenacyl) arabinofuranosyluracil.

N3-(2',5 '-Dimethoxyphenacyl)arabinofuranosyluracil (N3-(2',5 '-DiMeOPhAc)AraU) is a pyrimidine nucleoside derivative which possesses antinociceptive effect by intracerebroventricular (i.c.v.) administration to mice. The compound (100 microM) significantly decreased the specific binding of [3H]D-Ala2, N-Me-Phe4, Gly5-ol-enkephalin (DAMGO) and [3H]D-Pen2, D-Pen5-enkephalin (DPDPE) at the mu- and delta-opioid receptor, respectively, but has no effect on the binding of [3H]U-69,593 at the kappa-opioid receptor of rat brain slices. The autoradiographic studies also demonstrated that [3H]DAMGO and [3H]DPDPE bindings on the rat brain slice were displaced by N3-(2',5'-DiMeOPhAc)AraU. These results indicate that N3-(2',5'-DiMeOPhAc)AraU interacts with mu- and delta-opioid receptors.