Optical density values were measured using Scion Image for Windows (Scion Corporation, Fredrick, MD) from digitalized images with a resolution of 300dpi (films scanned by Microtek ScanMaker III, Düsseldorf, Germany) or FLA3000 (FUJIFILM, Stamford, CT). The optical density values were converted to DPM (disintegrations per minute)/mg by reference to co-exposed 14C standards (American Radiolabeled Chemicals, St. Louis, MO). Measurements were taken within striatal subregions (caudate, putamen, nucleus accumbens (NAc) core and shell) aided by published atlas of the primate striatum.32 Dpm/mg values from duplicate slides were averaged and used for statistical calculations.
