Fig 1: DA source in the cerebellum.a Dual immunostaining of CYP2D and CB. Six biological replicates were performed. Scale bar, 500 µm (upper) and 20 µm (lower). b Dual immunostaining of GFP and S100β. CAG-dLight1.1-GFP was expressed in the cerebellum. Three biological replicates were performed. Scale bar, 400 µm (inset, 50 µm). c dLight1.1 signals induced by DA at different concentrations (n = 3 slices/1 mouse) and blocked by SCH23390. The solid red box shows ROIs where dLight1.1 signals were measured; the dashed white box indicates background signals. d dLight1.1 signals evoked by electrical stimulus were recorded before and 15 min after SCH23390 application (n = 4 slices/2 mice). Scale bar, 50 µm. The solid red box shows ROIs; the dashed blue box indicates background signals. The orange arrow points to the placement of the stimulus electrode. e dLight1.1 signals evoked in slices perfused with normal aCSF (n = 10 slices/3 mice), in slices pretreated with fluoxetine (n = 10 slices/3 mice), or in slices from mice administered with fluoxetine (n = 11 slices/3 mice). Data are presented as mean ± SEM. Kruskal–Wallis test with Dunn’s multiple comparisons test (p = 0.0003, Con vs. In vitro fluo; p = 0.003, Con vs. In vivo fluo). f Dual immunostaining of mCherry and GFP. Example trace of a whole-cell recording was acquired from a hM3D(Gq)-expressing PC. Scale bar, 20 µm. g dLight1.1 signals induced by CNO application (n = 17 slices/5 mice). The solid line indicates the mean, and the shaded area shows the SEM. Unpaired Student’s t test (p = 0.0357, baseline vs. 6 min after CNO). h dLight1.1 signals were recorded before and 10 min after reserpine application (n = 7 slices/3 mice). Data are presented as mean ± SEM. Two-sided Wilcoxon matched pairs signed rank test (p = 0.0156, Pre vs. Post). i In vivo dLight1.1 signals recorded in the cerebellum (n = 22 recordings/5 mice) and striatum (n = 6 recordings/3 mice). Data are presented as mean ± SEM. Unpaired two-sided Student’s t test (p < 0.0001, Hz Cb vs. Str; p = 0.0064, Fluorescence Cb vs. Str). The cartoon was created with BioRender.com.