2.5. HPLC Analysis of Dopamine Content

The tissue levels of noradrenaline (NA), dopamine, 5-hydroxytryptamine (serotonin; 5-HT), 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) were measured using high-performance liquid chromatography with electrochemical detection (HPLC-EC). The concentrations of endogenous dopamine and its metabolites (DOPAC, HVA) were measured using HPLC-EC, according to a previously described method [35]. Briefly, sections including striatum and cortex were isolated by the mouse brain matrix in the region between Bregma 1.42 mm and −0.10 mm. Average tissue weight was approx. 50 mg. After weighing, the tissue samples were deep frozen in dry ice, stored at −80 °C until further use, and processed as previously described [16].