Only data from rats with verified probe placements were included in the analysis. Dialysates were analyzed for the levels of DA and its metabolites using an HPLC system. The mobile phase consisted of 0.1 M NaOAc, 0.1 M citric acid, 200 mg/l 1-octane-sulfonic acid, 10 mg/l 2Na-EDTA and 12% methanol.