Imaging of serotonin and dopamine transporters in the living human brain.

Alterations in brain serotonin (5-HT) and dopamine (DA) activity are associated with several neuropsychiatric disorders, but until now it has not been possible to simultaneously visualize or quantify the 5-HT and the DA transporter density in the living human brain. In this paper we report on the imaging of 5-HT and DA transporters in 28 healthy controls with single-photon emission tomography using iodine-123 labelled 2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane ([123I] beta-CIT) as the tracer. The [123I] beta-CIT distribution showed the most prominent 5-HT activity in the medial frontal cortex, hypothalamus, midbrain and occipital cortex and the greatest DA activity in the basal ganglia. The specific binding of the 5-HT transporters in the medial frontal cortex was 0.377 +/- 0.031 and that of the DA transporters in the basal ganglia, 0.916 +/- 0.007. Gjedde-Patlak plots indicated two separate components: the first was assumed to represent 5-HT transporters with a slope of 1.29 +/- 0.27 h-1 and the second, DA transporters with a slope of 0.30 +/- 0.04 h-1. This distinct kinetic pattern and the fact that 5-HT and DA transporters are situated in different parts of the brain provides an opportunity to study in vivo patients suffering from various neuropsychiatric disorders.