In vivo binding of the dopamine-1 receptor PET tracers [ ¹¹C]NNC112 and [¹¹C]SCH23390: A comparison study in individuals with schizophrenia

Rationale: A deficit in dopamine-1 (D₁) receptor function in the prefrontal cortex is suggested to play a role in the cognitive dysfunction observed in patients with schizophrenia. However, the results from positron emission tomography imaging studies of D₁ receptor levels in individuals with schizophrenia are mixed. Objectives: The aim of this investigation was to determine whether the in vivo characteristics of the different D₁ receptor tracers used in previous reports, [ ¹¹C]SCH23390 and [¹¹C]NNC112, may have contributed to these discrepancies reported in the literature. Methods: Eight patients with schizophrenia and 12 healthy control subjects were scanned with both [ ¹¹C]SCH23390 and [¹¹C]NNC112. Results: [ ¹¹C]SCH23390 and [¹¹C]NNC112 binding potentials in both patients and control subjects were compared and no tracer by diagnosis interactions were observed. Conclusions: The results of this study suggest that differences in the binding of [¹¹C]SCH23390 and [¹¹C] NNC112 observed in previous studies are not due to differences in the in vivo behavior of these tracers.