Striatal amphetamine-induced dopamine release in patients with schizotypal personality disorder studied with single photon emission computed tomography and [123I]iodobenzamide

Background Previous imaging studies demonstrated that schizophrenia is associated with increased amphetamine-induced dopamine (DA) release in the striatum, most pronounced during episodes of illness exacerbation. Schizotypal personality disorder (SPD) is a schizophrenia spectrum disorder, genetically related to schizophrenia. The goal of this study was to investigate striatal DA function in patients with SPD. Methods In our study, 13 SPD patients and 13 matched healthy control subjects underwent single photon emission computed tomography (SPECT) scan during bolus plus constant infusion of the D2/3 radiotracer [123I]iodobenzamide (IBZM). Striatal specific to nonspecific equilibrium partition coefficient (V₃′′) was measured at baseline and following amphetamine administration (.3 mg/kg). Results No significant differences were observed in baseline V₃′′ between groups. Amphetamine induced a larger decrease in [123I]IBZM V ₃′′ in SPD patients (-12 ± 5%) compared with control subjects (-7 ± 5%, p = .03). Conclusions The reduction in [123I]IBZM V₃′′ induced by amphetamine in SPD was similar to that observed in remitted schizophrenia patients (-10 ± 9%, n = 17), but significantly lower than that observed during illness exacerbation (-24 ± 13%, n = 17). This suggests that DA dysregulation in schizophrenia spectrum disorders might have a trait component, present in remitted patients with schizophrenia and in SPD, and a state component, associated with psychotic exacerbations but not SPD.