Synthesis and in vivo evaluation of [18F]-N-(p-nitrobenzyl)spiperone ([18F]PNBS) in rats.

[18F]-N-(p-nitrobenzyl)spiperone, [18F]PNBS, was prepared and its in vivo uptake in rat brain was measured. A temporal increase in striatum:cerebellum ratio and frontal cortex:cerebellum (FC:Cb) ratio was observed. Blocking studies suggested the formation of a radiolabeled metabolite, presumably [18F]spiperone, that is capable of crossing the blood-brain barrier and labeling cortical 5-HT2 receptors. This was confirmed using the ISRP method of metabolite analysis indicating [18F]PNBS is not a suitable tracer for studying D2 receptors in vivo with PET.