SEROTONERGIC MODULATION OF STRIATAL D-2 DOPAMINE-RECEPTOR BINDING IN HUMANS MEASURED WITH POSITRON EMISSION TOMOGRAPHY

The modulating effect of serotonergic drugs on the striatal dopamine n eurotransmission has remained controversial, and there are no publishe d data on serotonin-dopamine interaction obtained from living human br ain. Citalopram is a selective serotonin reuptake inhibitor widely use d in the treatment of depression (20-40 mg/day). We measured the effec ts of acute (20 mg, per os) and chronic (20 mg/day for 14 days) doses of citalopram and placebo intake on [C-11]-raclopride binding to stria tal D-2-receptors in eight healthy volunteers by using positron emissi on tomography. Although the effect magnitude was not large, the result s indicate that chronic citalopram intake slightly decreases the raclo pride binding which may reflect increased dopamine release in the stri atum. In addition, after 14 days there was a high correlation between the citalopam plasma levels and the decrease in the [C-11]-raclopride binding in both the caudate and the putamen, although statistically si gnificant effect in the raclopride binding potential was more pronounc ed in the putamen. This report suggests functional interaction of brai n dopaminergic and serotonergic systems in vivo in man.