INCREASED STRIATAL DOPAMINE TRANSMISSION IN SCHIZOPHRENIA - CONFIRMATION IN A 2ND COHORT

Objective: The authors previously observed an increase in striatal dop amine transmission following amphetamine challenge in 15 untreated pat ients with schizophrenia compared to 15 matched healthy subjects. The purpose of this study was to replicate this finding in a new cohort of schizophrenic patients and healthy subjects. Method: Fifteen patients with schizophrenia and 15 healthy subjects matched for age, gender, e thnicity, and parental socioeconomic status were recruited for this st udy. Patients fulfilled DSM-IV criteria for schizophrenia, had no hist ory of alcohol or substance abuse or dependence, and were neuroleptic free for a minimum of 21 days. Amphetamine-induced dopamine release wa s assessed by the reduction in dopamine Da receptor availability induc ed by an acute amphetamine challenge (0.3 mg/kg, intravenous bolus). R eduction in D-2 receptor availability was measured with single photon emission computed tomography and the D-2 receptor radiotracer [I-123]I BZM. Results: No differences were observed between patients with schiz ophrenia and the comparison group in D-2 receptor availability at base line. Patients with schizophrenia exhibited a significantly larger red uction in D-2 receptor availability following acute amphetamine challe nge than the comparison group. In this study, the effect size was smal ler than in the first study. Excess dopamine release following ampheta mine was associated with transient emergence or worsening of positive symptoms. Conclusions: In this new cohort of subjects the authors repl icated their initial observation of a dysregulation of striatal dopami ne release in schizophrenia.