SYNTHESIS AND IN-VIVO EVALUATION OF A NEW F-18 LABELED DOPAMINE-D2 RADIOLIGAND WITH BENZOFURAN BENZAMIDE SKELETON

]fluoroethyl)-2,3-dihydroben-zofuran-7-carboxamide ([F-18]5) was synth esized via nucleophilic substitution with (KF)-F-18/Kryptofix222 compl ex in 5.4 approximately 6.8% radiochemical yields with a specific acti vity of larger than 5.6 TBq/mmol (150 Ci/mmol) at the end of the 110 m inutes synthetic period. Its in vivo affinity toward CNS dopamine D2 r eceptors was investigated using rats in order to evaluate as a radiotr acer for the PET (positron emission tomography) study of the dopamine D2 receptors. In biodistribution experiments, [F-18]5 exhibited striat al accumulation, although the whole brain radioactivity was cleared ra pidly. The striatal/cerebellar radioactivity ratio, which corresponds to the ratio of a brain D2 receptor-rich to poor region, gradually inc reased to about 12 at 60 minutes after the injection. The striatal upt ake was inhibited with pretreated haloperidol, a dopamine D2 antagonis t, indicating that the striatal accumulation was due to the specific b inding with D2 receptors. Thus, [F-18]5 appears to be a potential in v ivo radiotracer for dopamine D2 receptors.