Acute treatment with clozapine blocks D1 dopamine receptor binding in discrete brain areas of the male rat

The ability of acute treatment with clozapine in vivo to block D1 receptors in the rat telencephalon and midbrain was investigated using the irreversible inactivation of [125I]SCH 23982 binding sites by N-ethoxy-carbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ; 6 mg/kg, i.p., 24 h). As analyzed by quantitative autoradiography, clozapine (40 mg/kg, i.p., 15 min before EEDQ administration) was found to produce a partial protection of central D1 receptors in all brain areas investigated, including cerebrocortical regions. These data could perhaps explain the failure of clozapine to induce tardive dyskinesia upon chronic treatment.