PET Study of the Effects of Valproate on Dopamine D₂ Receptors in Neuroleptic- and Mood-Stabilizer-Naive Patients With Nonpsychotic Mania

OBJECTIVE: A previous study reported a higher than normal density of dopamine D₂ receptors in psychotic mania but not in nonpsychotic mania. The purpose of this study was to further examine D₂ receptor density in a larger sample of nonpsychotic manic patients by using positron emission tomography (PET) and [¹¹C]raclopride. METHOD: Thirteen neuroleptic- and mood- stabilizer-naive patients with DSM-IV mania without psychotic features and 14 healthy comparison subjects underwent [¹¹C]raclopride PET scans. Of the 13 patients, 10 were treated with divalproex sodium monotherapy. PET scans were repeated 2–6 weeks after commencement of divalproex sodium. D₂ receptor binding potential was calculated by using a ratio method with the cerebellum as the reference region. RESULTS: The [¹¹C]raclopride D₂ binding potential was not significantly different in manic patients than in the comparison subjects in the striatum. Treatment with divalproex sodium had no significant effect on the [¹¹C]raclopride D₂ binding potential in manic patients. There was no correlation between the D₂ binding potential and manic symptoms before or after treatment. CONCLUSIONS: These results suggest that D₂ receptor density is not altered in nonpsychotic mania and that divalproex sodium treatment does not affect D₂ receptor availability.