PET scans were acquired by an Inveon PET scanner (Siemens Medical Solutions, Knoxville, TN, USA). Sprague-Dawley rats were kept under anesthesia with 1–2% (v/v) isoflurane during the scan. The radiotracer (ca. 1 mCi/150–200 μL) was injected via a preinstalled catheter via tail vein. A dynamic scan in 3D list mode was acquired for 90 min. For pretreatment studies, 10 (3 mg/kg), KML29 (3 mg/kg) or URB597 (3 mg/kg) dissolved in 300 μL saline containing 5% ethanol, 5% DMSO and 5% Tween® 80 was injected at 30 min via the tail vein catheter before the injection of 16. For displacement (“chase”) studies, KML29 (3 mg/kg) was injected at 15 min via the tail vein catheter after the injection of 16. As we previously reported,46 (link), 90 (link), 91 (link) the PET dynamic images were reconstructed using ASIPro VW software (Analysis Tools and System Setup/Diagnostics Tool, Siemens Medical Solutions). Volumes of interest, including the whole brain, cerebral cortex, cerebellum, striatum, thalamus and pons were placed referencing the MRI template software. The radioactivity was decay-corrected and expressed as the standardized uptake value. SUV = (radioactivity per mL tissue/injected radioactivity) x body weight.