P-[F-18]FLUOROBENZYLTROZAMICOL ([F-18]FBT) - MOLECULAR DECOMPOSITION RECONSTITUTION APPROACH TO VESAMICOL RECEPTOR RADIOLIGANDS FOR POSITRON EMISSION TOMOGRAPHY

Current methods of radioligand synthesis for the vesamicol receptor ei ther utilize bioactive unlabeled precursors and/or generate unlabelled bioactive by-products. The presence of these compounds in the radiotr acer preparation increases the risk of adverse pharmacological reactio ns in animals. To eliminate the risk of such reactions, we have synthe sized the novel radioligand [F-18]FBT from two inactive precursors, [F -18]fluorobenzyl iodide and trozamicol. (+)- and (-)-[F-18]FBT were sy nthesized in 57-85% yield, from [F-18]fluorobenzyl iodide and (+) and (-)-trozamicol, respectively. In the rat brain, comparable levels of ( -)-[F-18]FBT were found in the striatum, cortex, cerebellum and hippoc ampus during a 3 h period. In contrast, the striatum:cerebellum, corte x: cerebellum and hippocampus: cerebellum ratios for (+)-[F-18]FBT inc reased from unity at 5 min post-injection to 2.8, 1.4 and 1.7, respect ively, at 3 h. Therefore, (+)-[F-18]FBT may be potentially useful for mapping vesamicol receptor density in vivo.