Iodoethylspiperone, a new potential agent for exploration of central dopamine D2 receptors: synthesis and preliminary in vivo study.

We synthesized a new spiperone derivative: iodoethylspiperone (IES) to perform dopamine D2 receptor exploration by SPECT. IES was prepared from a precursor: tosylethylspiperone, and characterized by i.r. and 1H-NMR analyses. [125I]IES was obtained with 80% yield. In vivo biodistribution in rats showed a high and specific uptake in the striatum. The uptake ratio between the striatum and the cerebellum reached a maximum value 4 h after injection (10.05 +/- 2.81). IES labeled with 123I should be a promising new agent to investigate D2 receptors in the living human brain.