3-N-(2-[18F]-fluoroethyl)-spiperone: a novel ligand for cerebral dopamine receptor studies with pet

3-N-(2-[18F]-fluoroethyl)-spiperone [( 18F]-FESP) was synthesized at high specific activity by condensation with 2-[18F]-fluoroethyltosylate (35 TBq/mmol). In vivo binding studies in baboons by positron emission tomography exhibited regio-selective uptake in the striatum which was saturable with the cold ligand and prevented by pretreatment with (+)-butaclamol. The pharmacokinetic behaviour, i.e. the absolute uptake in tissue and the striatum-to-cerebellum ratio, was very similar to that of methylspiperone. Analysis of the radioactivity in mouse brain after administration of [18F]-FESP indicated a high in-vivo stability (greater than 90% after 210 min in the striatum). Comparative distribution studies of other N-fluoroalkylspiperones in mice suggest that FESP and the N-fluoropropyl analogue are the most potent D2 receptor ligands.