Autoradiographic localization of D1 and D2 dopamine binding sites in the human retina

The localization of dopamine binding sites was studied by in vitro autoradiography in the normal human retina using [125I]SCH 23982 for D1 receptor labelling and [125I]iodosulpride for D2 receptors. Results demonstrated that both types of binding sites were present in human retina. Binding of [125I]SCH 23982 to D1 dopamine receptor was blocked by 1 microM SKF 38393, SCH 23390 (D1 specific compounds) whereas bromocriptine and domperidone (D2 specific compounds) were inactive at the same concentration. On the contrary, binding of [125I]iodosulpride to D2 dopamine receptor was inhibited only by D2 drugs. Precise cellular distribution was given by microautoradiographic techniques and showed that binding sites were exclusively localized to the plexiform layers.