Presynaptic dopaminergic function in the striatum of schizophrenic patients

The dopaminergic hypothesis of schizophrenia postulates increased brain dopaminergic activity. Two previous studies reported increased F-18-DOPA uptake with positron emission tomography in schizophrenic patients (n=5, n=7). In the present study, striatal dopaminergic function was assessed in vivo in six untreated schizophrenics and seven control subjects, comparable for age and sex. The F-18-fluoro-L-DOPA (F-18-DOPA) uptake rate constant K-i was determined in the caudate and putamen using coregistered positron emission tomography and magnetic resonance imaging. No difference between groups for mean K-i was found. The variability of the F-18-DOPA uptake values was higher in the caudate (p<0.01) and in the putamen (p<0.001) in schizophrenic patients than in control subjects, suggesting that schizophrenia is a disorder involving heterogeneous states of the striatal presynaptic dopaminergic function.