Quantitative analysis of structural elements of MFBs
| Bouton | Active zones | Cleft width | Excrescences | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Volume (μm3) | Surface (μm2) | Contact area to postsynaptic target [μm2 (%)] | No. | Mean area ± SD (μm2) | Total area [μm2 (%)] | Distance to neighboring AZ ± SD (μm) | AZ ± SD (nm) | PA ± SD (nm) | No. | Total area (μm2) | PSD area [μm2 (%)] | |
| P28 | ||||||||||||
| 1 | 6.02 | 42.00 | 21.14 (50.3) | 19 | 0.11 ± 0.06 | 2.05 (9.7) | 0.44 ± 0.24 | 30.29 ± 4.10 | 27.68 ± 2.56 | 2 | 13.00 | 1.77 (13.6) |
| 2 | 8.16 | 105.70 | 41.22 (39.0) | 37 | 0.09 ± 0.04 | 3.40 (8.2) | 0.42 ± 0.27 | 31.90 ± 5.13 | 29.12 ± 1.45 | 7 | 30.00 | 2.85 (9.5) |
| 3 | 5.05 | 48.40 | 20.68 (42.7) | 18 | 0.13 ± 0.10 | 2.39 (11.6) | 0.42 ± 0.15 | 30.93 ± 2.82 | 19.78 ± 2.10 | 5 | 14.90 | 2.36 (15.8) |
| 4 | 9.15 | 106.00 | 48.33 (45.6) | 45 | 0.12 ± 0.08 | 5.49 (11.4) | 0.33 ± 0.16 | 30.69 ± 5.27 | 25.63 ± 2.64 | 9 | 35.90 | 5.07 (14.1) |
| Mean | 7.10 | 75.53 | 32.84 (44.4) | 29.75 | 0.12 ± 0.10 | 3.33 (10.2) | 0.40 ± 0.20 | 30.95 ± 1.13 | 25.55 ± 0.55 | 23.45 | 3.01 (13.3) | |
| CV | 0.27 | 0.46 | 0.43 (0.1) | 0.83 | 0.46 (0.20) | 0.49 | 0.04 | 0.02 | 0.48 | 0.48 (0.20) | ||
| Adult | ||||||||||||
| 1 | 13.03 | 82.19 | 31.56 (38.4) | 34 | 0.07 ± 0.05 | 2.26 (7.2) | 0.32 ± 0.09 | 28.11 ± 3.26 | 19.62 ± 2.63 | 4 | 20.90 | 2.12 (10.1) |
| 3 | 5.42 | 50.55 | 21.00 (41.9) | 14 | 0.14 ± 0.13 | 2.01 (9.5) | 0.52 ± 0.14 | 29.46 ± 5.22 | 20.25 ± 2.58 | 5 | 14.00 | 1.24 (8.8) |
| 4 | 12.17 | 68.90 | 24.13 (35.0) | 18 | 0.17 ± 0.10 | 3.06 (12.7) | 0.60 ± 0.27 | 19.74 ± 0.65 | 20.66 ± 3.20 | 7 | 20.00 | 2.68 (13.4) |
| 7 | 2.35 | 32.37 | 11.39 (35.2) | 7 | 0.15 ± 0.08 | 1.07 (9.4) | 0.47 ± 0.27 | 29.81 ± 3.09 | 20.48 ± 0.44 | 3 | 9.22 | 0.91 (9.9) |
| Mean | 8.24 | 58.50 | 22.07 (37.6) | 18.25 | 0.11 ± 0.07 | 2.10 (9.7) | 0.48 ± 0.19 | 26.78 ± 1.87 | 20.25 ± 1.21 | 16.03 | 1.74 (10.6) | |
| CV | 0.63 | 0.37 | 0.38 (0.1) | 0.64 | 0.39 (0.20) | 0.40 | 0.07 | 0.06 | 0.34 | 0.47 (0.20) | ||
Summary of structural parameters relevant for synaptic transmission that have been extracted from the detailed 3-D reconstructions of MFBs in P28 and adult rats. The quantifications of two additional very small boutons (surface area of 8.2 and 13.9 μm2; contact area to postsynaptic target of 4.5 and 2.3 μm2; and a pool size of 2533 and 2795, respectively) were not included because they may resemble satellites (Galimberti et al., 2006) or belong to filopodia. The values of the cleft width of AZs and PAs were taken from measurements at the center of both membrane specializations (see also text). The means and CVs given in this table are averages per bouton.