Vesicular monoamine transporter concentrations in bipolar disorder type I,schizophrenia, and healthy subjects

Background: Previous analyses of vesicular monoamine transporter (VMAT2) bi nding in euthymic bipolar disorder type I (BDI) patients have shown increas es of this presynaptic marker in the thalamus and ventral midbrain. To asse ss the diagnostic specificity of those findings, Mle compared VMAT2 concent rations between euthymic BDI patients, patients diagnosed with schizophreni a (SCH), and age-matched healthy volunteers. Methods: Binding sites far VMAT2 were quantified with (+)-alpha-[C-11]DTBZ (dihydrotetrabenazine) and positron emission tomography. Fifteen euthymic B DI and 12 SCH patients and 15 group-matched healthy controls were studied [ C-11]DTBZ tracer transport and binding potentials were examined in the thal amus and ventral midbrain with factorial analyses of variance and post hoc Tukey's honestly significantly different tests. Results: Analysis of variance detected diagnosis effects in binding potenti als in both brain regions. Binding of VMAT2 in the thalamus was higher in B DI patients than in control subjects and SCH patients, Conversely: ventral brainstem binding was nearly identical between BDI and SCH patients and wer e higher than in the control group. Conclusions: The patterns of regional VMAT2 expression, and by extension, t he concentration of monoaminergic synaptic terminals, differ between BDI, S CH, and a control group. These findings may relate to both similarities and differences in the presentation or clinical course of these syndromes and require further examination. (C) 2001 Society of Biological Psychiatry.