Identification and initial characterization of high-affinity [ 3H]dextrorphan binding sites in rat brain

We have identified specific high-affinity [ 3H]dextrorphan binding sites in rat forebrain. [ 3H]Dextrorphan binds saturably and reversibly to an apparently homogeneous class of sites characterized by a B max of 2.62±0.06 pmol/mg protein and K D of 60±4 nM. Glycine and glutamate independently increase [ 3H]dextrorphan binding in a concentration-dependent manner. The pharmacological profile of [ 3H]dextrorphan binding characterized by equilibrium competition experiments, together with these data suggest that [ 3H]dextrorphan labels a site at or near the N-methyl-D-aspartate receptor.