Radioiodinated 2′-iodospiperone: A new radioligand for in vivo dopamine receptor study

In vivo dopamine receptor binding of the newly synthesized ligand, 125I-2′-iodospiperone (125I-2′-ISP), was studied in mouse brain. The highest accumulation was found in the striatum. Analysis of the striatal homogenate showed the 125I-2′-ISP to be metabolically stable. Furthermore, this striatal binding was saturable and displaced only by dopaminergic drugs. On the other hand, the accumulation in the cortex was as low as that of the cerebellum and uneffected by the administration of serotoninergic drugs and dopaminergic drugs; results assessed by macroautoradiographic studies. Thus, the newly synthesized 125I-2′-ISP presented high affinity for dopamine receptors in vivo and therefore, holds great potential for the in vivo dopamine receptor studies, provided 123I becomes readily available.