Longitudinal PET Imaging of Antipsychotic Binding to the Dopamine-3 Receptor in Schizophrenia

This is a clinical trial in which 40 participants with schizophrenia will be randomized to 15 days of treatment with cariprazine (CAR) or brexpiprazole (BREX) in a single-blind manner. \[11C\]PHNO PET scans will be obtained before treatment and after 1 day and 15 days of treatment to examine the effects of antipsychotic medications on the dopamine-3 receptor (D3R). The overall objectives of the current study are to: 1) measure the acute binding of CAR/BREX to the D3R; 2) measure D3R availability for evidence of upregulation following subchronic administration of CAR/BREX in the same set of patients; 3) examine relationships between subchronic binding of CAR/BREX to, and upregulation of, the D3R vs. D2R and changes in positive symptoms, negative symptoms, and cognitive deficits. Relationships between subchronic binding of CAR/BREX and EPS will be explored.