Localisation and pharmacological characterisation of D-2 dopamine receptors in rat cerebral neocortex and cerebellum using [125I]iodosulpride.

Dopamine D-2 receptors were characterised in membranes from all areas of rat cerebral cortex and from cerebellum tested, by using [125I]iodosulpride, a highly selective ligand. The IC50 values of a large variety of dopaminergic and non-dopaminergic agents against [125I]iodosulpride binding in parietal cortex or cerebellum were highly correlated with their IC50 values against [125I]iodosulpride (or [3H]domperidone) binding in striatum. Moreover in the presence of a guanylnucleotide, 5'-guanylylimidodiphosphate (GppNHp), the dopamine inhibition curves of [125I]iodosulpride binding were shifted similarly to the right in the three regions. The density of D-2 receptors in cerebellum and in most areas of the cerebral cortex represented about 1% and 2%, respectively, of their density in striatum whereas the corresponding value in frontal cortex was 4%. Labelling on autoradiographic sections was localised to superficial (I-III) and deep layers (V) of the parietal cortex and to the molecular layer of the cerebellum.