Fig. 2: Somatodendritic optogenetics reveals unaltered STD DA release in the absence of Syt1.
A Immunohistochemistry in brain slices of adult Syt1 cKODA mice infected with AAV2/5-hsyn-DIO-ChR2-eYFP-Kv (n = 4 mice, one representative set of images is shown), showing expression of ChR2-Kv (eYFP) in the whole ventral mesencephalon (scale bar = 500 µm) and striatum (scale bar = 1 mm) using epifluorescence microscopy at ×20. B Expression of ChR2-Kv in the same mice evaluated by confocal microscopy at ×60 shows infected DA neurons (TH) in the midbrain (top panel, scale bar = 50 µm). Optical zoom and z-stack on an infected DA neuron showing the membrane distribution of the eYFP signal (bottom panel, scale bar = 10 µm, insert in the merge image shows the eYFP signal at a single focal plane). Evaluation of the eYFP signal in the striatum shows no axonal processes in the dorsal sector but a small contingent of positive fibers in the ventral sector of the striatum (scale bar = 50 µm). C–E Fast-scan cyclic voltammetry recordings with average [DA]o peaks obtained in the dorsal striatum (C), ventral striatum (D) and VTA (E) slices of infected Syt1+/+ and Syt1−/− mice with AAV2/5-hsyn-DIO-ChR2-eYFP-Kv (ChR2-Kv, n = 14 slices/7 mice in Syt1+/+, n = 17 slices/9 mice in Syt1−/−) or AAV5-EF1a-DIO-hChR2(H134R)-eYFP (control hChR2, n = 10 slices/5 mice). Representative traces for the striatum (dorsal + ventral) and VTA are shown in (F) and (G). DA release was optically triggered in each region using pulse-train stimulation (30 pulses of 470 nm blue light at 10 Hz) in ACSF containing 5 µM of nomifensine and sulpiride. H TTX (1 µM) effect on average [DA]o peaks in the striatum and the VTA (% of inhibition) (n = 14 slices/7 mice in Syt1+/+, n = 17 slices/9 mice in Syt1−/−). Error bars represent ± SEM and the statistical analysis was carried out by two-way ANOVA followed by Šidák (E) and Tuckey (C, D, H) tests (ns, non-significant; *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001). Source data are provided as a Source Data file.
