Presynaptic active zones are reduced by accumulating α-syn. (A) Confocal images of NMJ, immunolabelled with anti-nc82/BRP and anti-HRP. (B) Dashed box represents the section of the NMJ (A) imaged with instant super resolution structured iSIM. (C) Quantitative analysis of total number of BRP puncta that represents the AZs labelled with anti-nc82/BRP per NMJ; *P = 0.0189 compared with nSyb/+ and *P = 0.0492 compared with nSyb>EGFP. (D) Number of BRP puncta normalized by the synaptic surface micrometres square immunolabelled with anti-HRP; *P = 0.0289 compared with nSyb/+ and *P = 0.03 compared with nSyb>EGFP. (E) The total number of synaptic boutons/NMJ was unchanged. All graphs are represented as mean ± SEM shown for each genotype (n = 8 flies for nSyb/+ and nSyb>EGFP; and nine flies for nSyb>WT-α-syn-EGFP). Statistical analyses were performed using one-way ANOVA test followed by Tukey’s multiple comparison post hoc test. Scale bars: (A) 10 µm and (B) 5 µm.