Presynaptic terminal | |
Length of active zone | 7.6 μm |
Area of active zone | 0.45 μm2 |
Syndesome | |
Number | 20 |
x/y ratio | 1.0 ± 0.08 (n = 28) |
Diameter (nm) | 59 ± 4.5 (n = 58) |
Center-to-center spacing (nm) | 106 (52%); 162 (35%); 232 (13%) |
Density (μm2 of active zone) | 44 |
Number of attached vesicles | 7 |
Synaptic vesicles | |
Total number of vesicles | 912 |
Total number of vesicles attached to syndesomes | 18% |
Vesicles attached to syndesome only (second tier) | 12% |
Vesicles attached to syndesome and active zone (first tier) | 7% |
Vesicles attached to syndesomes and hemifused | 4% |
First tier vesicles that were hemifused | 57% |
Hemifused vesicles attached to two syndesomes | 1% |
Fully fused vesicles | 0.5% |
The table summarizes data collected from 17 reconstructions of rat neocortical synapses. The number of syndesomes (20) and vesicles (912) refer to ″complete″ organelles after correcting for those that are incomplete and located at the edges of the sections.