Brains were isolated and nigrostriatal tissue collected for further analysis. Tissue was homogenized in ice-cold 0.3 M perchloric acid and stored at −80°C. Prior to HPLC analysis, the homogenate was centrifuged at 10,000 g for 10 min and supernatant injected into the HPLC for neurochemistry analysis. The weight of tissue collected was used to normalize the pmol of dopamine and dopamine metabolites detected to mg of tissue. Dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylacetaldehyde (DOPAL), were analyzed via an Agilent 1100 Series capillary HPLC system with an ESA Coulochem III coulometric electrochemical detector (Enayah et al., 2018 (link)). Separation was achieved with a Phenomenex Synergi C18 column (2 × 150 mm, 40 Å) using an isocratic mobile phase (50 mM citric acid, 1.8 mM sodium heptane sulfonate, 0.2% trifluoroacetic acid, 2% acetonitrile, pH = 3.0) at 200 μL/min. For electrochemical detection of catechol-containing compounds, the guard cell, electrode 1, and electrode 2 were set to +350, −150, and +200 mV, respectively.