[3H]dopamine binds to D-1 and D-2 receptors in rat striatum

Although saturation studies suggest that [3H]dopamine binds to a homogeneous class of stereospecific sites in rat striatal membranes, pharmacologic analysis reveals two distinct sites, one with high and another with low antagonist affinities. The affinity of antagonists for the first site is correlated with their affinity for [3H]butyrophenone binding sites; affinity for the second site is correlated with inhibitory potency against the dopamine-stimulated adenylate cyclase. These results suggest that [3H]dopamine binds to D-1 and D-2 receptors.