RELATIVE AFFINITIES OF DOPAMINERGIC DRUGS AT DOPAMINE D-2 AND D-3 RECEPTORS

Quantitative autoradiography was used to evaluate the pharmacological profile of dopamine D-2-like receptors labeled by [I-125]iodosulpiride . Caudate/putamen, a brain region associated primarily with dopamine D -2 receptor mRNA, was used as a prototypical D-2 tissue; cerebellar lo bule X (D-3 mRNA associated), as a D-3 tissue. 7-OH-DPAT opylamino-7-h ydroxy-1,2,3,4-tetrahydronaphthalene) exhibited selectivity for cerebe llar receptors (24-fold), followed by quinpirole (6-fold). Haloperidol and domperidone were 4- and 18-fold more potent at striatal receptors , respectively. These data are in close agreement with that derived fr om dopamine D-2 and D-3 receptor-expressing cell lines.