Comparison of D2 and D3 dopamine receptor affinity of dopaminergic compounds in rat brain

This study used quantitative autoradiography to simultaneously evaluate the relative affinities of dopaminergic compounds for dopamine D2 and D3 receptors in rat brain. PD 152255, PD 128907, and l-nafadotride exhibited significantly higher affinity for cerebellar dopamine D3 sites than [3H]quinpirole-labeled sites in caudate/putamen (6.3-, 6.0-, and 2.3-fold, respectively). In contrast, chlorpromazine, risperidone, and domperidone were more potent at striatal dopamine D2 receptors (3.8-, 31-, and 40-fold, respectively). Dopamine, quinelorane, (+)-UH 232, and RS-trans-7-OH-PIPAT exhibited relatively little D2/D3 selectivity.