Fig 1: Quality control of synaptosomes enrichment. (A) Graphical image of the Percoll gradient for synaptosome enrichment. (B,C): Transmission electron microscopic analysis of density gradient fraction 15/23% Percoll at 10,500× (B) or 60,000× (C) magnification. At 10,500× magnification, no organelle contaminations could be observed but enrichment of synaptosomes (arrows) was obvious (B). Analysis at higher magnification showed synaptosomes contained mitochondria (asterisk) besides vesicles, underlining that synaptosomes resemble synapses. (D) Western blot analysis of different Percoll gradient fractions. Percoll fraction 15/23% did not contain astrocytes (indicated by GFAP) or microglia (indicated by AIF-1) and was identified as the purest synaptosomal fraction for further analysis.