Characterization of stereospecific binding of 3H-(-) sulpiride, a selective antagonist at dopamine-D2 receptors, in rat CNS.

Sulpiride endowed with dopamine (DA)-antagonist properties, does not antagonize neostriatal DA-sensitive adenylyl cyclase activity either in vitro or in vivo. Sulpiride however is able to displace radioactive ligands, which label DA-receptors, from their specific binding sites. On these bases sulpiride has been proposed as a selective antagonist at dopamine-D2 receptors. We have characterized 3H(-) sulpiride stereospecific binding in various rat brain areas. In particular, 3H(-) sulpiride binding was found to be saturable, stereospecific and maximally enriched in the synaptic membrane fraction prepared from dopaminergic brain areas. Among a variety of compound tested only DA, DA-agonists and DA-antagonists were competitors for 3H(-) sulpiride specific binding sites. The results suggest that 3H(-) sulpiride may be an useful tool for the characterization and localization of dopamine D2-receptors.