Increased platelet vesicular monoamine transporter density in adult schizophrenia patients.

Vesicular monoamine transporter (VMAT2) plays a major role in the synaptic accumulation and release of monoamines. In the present study, we assessed high affinity [(3)H]dihydrotetrabenazine binding to platelet VMAT2 in a group of treated (n = 9) and untreated (n = 4) patients with schizophrenia and age- and sex-matched controls. Significantly elevated platelet VMAT2 density (B(max)) (53%, P<0.0001) was observed in the mixed population of schizophrenia patients. The affinity of the ligand (K(d)) to platelet VMAT2 was similar in both groups. The increased platelet VMAT2 density may indicate a schizophrenia-related hyperactivity of the monoaminergic system or an adaptive response to chronic drug treatment.