No Evidence of Altered In Vivo Benzodiazepine Receptor Binding in Schizophrenia

Abstract Deficits in gamma-amino-butyric acid (GABA) neurotransmitter systems have been implicated in the pathophysiology of schizophrenia for more than two decades. Previous postmortem and in vivo studies of benzodiazepine (BDZ) receptor density have reported alterations in several brain regions of schizophrenic patients. The goal of this study was to better characterize possible alterations of the in vivo regional distribution volume (V T ) of BDZ receptors in schizophrenia, using the selective BDZ antagonist [ 123 I]iomazenil and single photon emission computerized tomography (SPECT). Regional BDZ V T was measured under sustained radiotracer equilibrium conditions. The reproducibility and reliability of this measurement was established in four healthy volunteers. No differences in regional BDZ V T were observed between 16 male schizophrenic patients and 16 matched controls. No relationships were observed between BDZ V T and severity of psychotic symptoms in any of the regions examined. In conclusion, this study failed to identify alterations of BDZ receptors density in schizophrenia. If this illness is associated with deficits in GABA transmission, these deficits do not substantially involve BDZ receptor expression or regulation.