Is the GABA System Related to the Social Competence Improvement Effect of Aripiprazole? An (18)F-Fluoroflumazenil PET Study

OBJECTIVE: Patients with schizophrenia who are treated with aripiprazole experience some benefits including an improvement of social competence, but the underlying mechanism of this improvement has not been investigated yet. This study aimed to provide preliminary evidence that the GABA system may be involved in the effect of aripiprazole on social competence. METHODS: Seventeen outpatients with schizophrenia (9 taking aripiprazole and 8 taking risperidone) and 18 healthy controls underwent (18)F-fluoroflumazenil PET, and GABA(A) receptor binding potential was compared between the three groups. RESULTS: Voxelwise one-way ANOVA showed that GABA(A) receptor binding potentials in the right medial prefrontal cortex (p=0.04) and right dorsolateral prefrontal cortex (p=0.02) were significantly lower in the aripiprazole group than the risperidone group, and those in the left frontopolar cortex (p=0.03) and right premotor cortex (p=0.02) were significantly lower in the aripiprazole group than the risperidone and control groups. CONCLUSION: Our results suggest that aripiprazole administration results in increased GABA transmission in the prefrontal regions, and that these increases may be a neural basis of aripiprazole's clinical benefits on an improvement of social competence.