AZ organization. (A) Number of proximal synaptic vesicles (SV; within 45 nm from the AZ) per synapse, which was significantly reduced in RIM1α KO synapses. (B) Average AZ area. A and B show mean values and SEMs (error bars). Confidence value: *, P < 0.05. The numbers of animals, synapses, and vesicles analyzed for each category are shown in Table S1. (C) Quantitative representation of AZ area (gray) per proximal vesicle (yellow), calculated as the total AZ area (B) divided by the number of proximal vesicles (A). Bar, 100 nm.