Associated Alterations of Striatal Dopamine D₂/D₃ Receptor and Transporter Binding in Drug-Naive Patients With Schizophrenia: A Dual-Isotope SPECT Study

OBJECTIVE: In vivo imaging studies have revealed deregulated presynaptic or postsynaptic function of the midbrain dopaminergic system in patients with schizophrenia. To further delineate the neuropathological involvement of the presynaptic and postsynaptic dopamine neurons in schizophrenia, the authors examined brain D₂-family receptor and dopamine transporter binding simultaneously in patients with drug-naive schizophrenia using the dual-isotope single photon emission computed tomography (SPECT) imaging technique. METHOD: Eleven patients with schizophrenia and 12 healthy comparison subjects were recruited. Striatal dopamine D₂/D₃ receptor was measured with SPECT and [¹²³I]iodobenzamide ([¹²³I]IBZM), while dopamine transporter was measured with SPECT and [^99mTc]TRODAT-1. RESULTS: Striatal D₂/D₃ receptor and dopamine transporter binding were unaltered in these drug-naive patients with schizophrenia. Nonetheless, D₂/D₃ receptor binding measures were positively correlated with dopamine transporter binding measures in these patients but not in the comparison subjects. CONCLUSIONS: The associated presynaptic and postsynaptic disturbances of midbrain dopamine neurons could be clinically relevant in drug-naive patients with schizophrenia.