RATIONALE: It has been suggested that the antipsychotic effect of antipsychotics is mediated by the antagonism of the dopamine D2 receptor in the limbic-cortical regions. Risperidone has an atypical property, but its effect on limbic-cortical regions has not been evaluated. OBJECTIVES: In this study, we examined the relationship among doses of risperidone and limbic-cortical dopamine D2 receptor occupancy using positron emission tomography. METHODS: Seven patients with schizophrenia were scanned during the steady state with risperidone. Their occupancies in limbic-cortical regions were determined using positron emission tomography with [11C]FLB 457. RESULTS: The average occupancy ranged from 38% to 80% on doses of 1-6 mg/day. The saturation curve plotted against the drug level fit the data well. CONCLUSIONS: Our results demonstrate that the D2 receptor occupancy with risperidone in the limbic-cortical regions seems to be similar to that of previous reports regarding the striatum, and it would be comparable to that of typical antipsychotics.
RATIONALE: It has been suggested that the antipsychotic effect of antipsychotics is mediated by the antagonism of the dopamine D2 receptor in the limbic-cortical regions. Risperidone has an atypical property, but its effect on limbic-cortical regions has not been evaluated. OBJECTIVES: In this study, we examined the relationship among doses of risperidone and limbic-cortical dopamine D2 receptor occupancy using positron emission tomography. METHODS: Seven patients with schizophrenia were scanned during the steady state with risperidone. Their occupancies in limbic-cortical regions were determined using positron emission tomography with [11C]FLB 457. RESULTS: The average occupancy ranged from 38% to 80% on doses of 1-6 mg/day. The saturation curve plotted against the drug level fit the data well. CONCLUSIONS: Our results demonstrate that the D2 receptor occupancy with risperidone in the limbic-cortical regions seems to be similar to that of previous reports regarding the striatum, and it would be comparable to that of typical antipsychotics.