SLC18A2 and Parkinson disease: The turnover rate of DA was increased, as measured via the metabolites 3,4-Dihdroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) (Fig. 5d right panel, one-way ANOVA, Tukey p < 0.05 vs. Ntg control littermate or WT); this might be similar to hu PD, which shows an increase in DA turnover correlated with VMAT2 loss38.