%0 Journal Article %A M. N. Tantawy %A T. E. Peterson %A J. M. Rook %A R. Baldwin %A M. S. Ansari %A R. M. Kessler %T Characterization of [18F]FPEB uptake in rats %D 2009 %J Journal of Nuclear Medicine %P 1187-1187 %V 50 %N supplement 2 %X 1187 Objectives MicroPET imaging of rats using [18F]FPEB (3-[18F]fluoro-5-(2-pyridinylethynyl)benzonitrile) can be used as a tool to study metabotropic glutamate receptor subtype 5 (mGluR5) occupancy in the brain. The main objectives of this study were to estimate K1, k2, kon, k4, and Bmax through kinetic modeling of microPET data with blood sampling. Methods Carotid and jugular catheters were implanted in 3 Sprague-Dawley (~300 g) rats 5 days prior to the start of the experiment. On the day of the experiment, each rat was anesthetized and positioned in the microPET Focus 220. A 90 min acquisition was started 30 sec prior to injection of ~15MBq/0.4 ml of [18F]FPEB via the jugular catheter. Blood samples were taken at multiple time points. The plasma was separated by centrifugation and measured in a well counter. Metabolite analysis was carried out by ethyl acetate extraction and thin layer chromatography to derive a corrected arterial input function. Using a within-subject design, the procedure was repeated one week later with the rats receiving an injection of 3 mg/kg MTEP, an mGluR5 antagonist, 30 minutes prior to radiotracer injection. Attenuation corrections were carried out using a 57Co transmission scan. Images were reconstructed using OSEM2D. Results The transfer rates were K1 = 0.19, k2= 0.2, kon = 0.001, k4 = 0.01, and Bmax = 24 using a two-tissue compartment model. Specific binding of FPEB was seen in the cerebellum, as evidenced by reduced uptake of FPEB following injection of MTEP. Conclusions No regions in the brain without specific binding of FPEB were observed. Occupancy measurements by kinetic modeling using [18F]FPEB in rats thus require metabolite corrected blood sampling. %U