Simultaneous Measurement of Dopamine Transporters and D 2 /D 3 Receptors in Drug Naïve Schizophrenic Patients

Objective: Previous single photon emission computed tomography (SPECT) studies have demonstrated that co-injection of radiotracers 99m Tc-TRODAT and 123 IBZM can assess both presynaptic, dopamine transporters (DATs), and postsynaptic, dopamine D 2 /D 3 receptors, markers of dopaminergic system simultaneously. The aim of this study was to determine both DATs and dopamine D 2 /D 3 receptors in drug naïve schizophrenic patients. Methods: Severn drug naïve schizophrenic patients and eleven age-matched healthy controls were recruited. Each subject received one SPECT measurement after intravenous co-administration of 99m Tc-TRODAT and 123 IBZM and one brain MRI scan. A ratio equilibrium model was applied to calculate the specific uptake ratio (SUR) which corresponds to the ratio of B max (receptor density) and K D (affinity). Results: The results showed that the SUR of DATs binding was not significantly different between healthy controls and drug naïve schizophrenic patients (2.92±0.62 vs. 2.65±0.27, p=0.052) and, however, the SUR of dopamine D 2 /D 3 receptors binding was significantly lower in drug naïve schizophrenic patients than those in healthy controls (2.79±0.54 vs. 3.90±0.58, p=0.001). Additionally, there was a significant correlation between left and right binding for both DATs (r=0.80, p=0.003) and dopamine D 2 /D 3 receptors (r=0.96, p=0.000) in healthy controls but not seen in drug naïve schizophrenic patients (r=0.54, p=0.20 for DATs, r=0.70, p=0.08 for dopamine D 2 /D 3 receptors). Conclusion: This study provides evidences to support the idea that abnormalities of dopaminergic system in schizophrenia and further elucidates the disruption of inter-hemispheric interaction of postsynaptic and presynaptic markers.