Table 1.
Ultrastructural characterization of synaptic boutons attached to hypoglossal motoneurons. Abbreviations: WT = wild‐type; S = spherical; F/P = flat/pleomorphic.
| WT | hSOD1G93A | |||
|---|---|---|---|---|
| S‐type | F/P‐type | S‐type | F/P‐type | |
| Covered perimeter (in percentage)† | 7.4 ± 0.8 (20) | 45.1 ± 4.0 (20) | 12.3 ± 1.4 (20)* | 19.7 ± 2.4 (20)** |
| Apposed membrane/bouton (µm)‡ | 1.11 ± 0.1 (85) | 1.42 ± 0.1 (492) | 1.38 ± 0.1 (128)* | 1.27 ± 0.0 (242)* |
| Detached membrane/bouton (in percentage)§ | 3.5 ± 1.4 (62) | 2.9 ± 1.1 (70) | 6.3 ± 1.7 (49) | 11.0 ± 2.0 (63)** |
| Boutons with active zone (in percentage) | 43.2 ± 7.3 | 48.8 ± 2.6 | 48.1 ± 5.7 | 46.3 ± 3.5 |
| No. of active zones/bouton | 1.32 ± 0.1 (31) | 1.38 ± 0.1 (41) | 1.26 ± 0.1 (27) | 1.17 ± 0.1 (29) |
| Active zone length (nm) | 179.0 ± 16.2 (41) | 160.6 ± 15.4 (58) | 149.6 ± 9.7 (34) | 121.0 ± 10.5 (33)* |
| No. of vesicles/µm2 near the active zone | 380.6 ± 34.7 (41) | 659.1 ± 40.1 (58) | 422.9 ± 23.3 (34) | 452.6 ± 59.2 (33)* |
| Vacuolated boutons (in percentage) | — | — | 10.8 ± 3.8 | 24.2 ± 3.8 |
*
P < 0.05;
**
P < 0.001, two‐way analysis of variance, post hoc Tukey's test.
†
Percentage of the motoneuron cell body perimeter covered by synaptic boutons.
‡
Average length per bouton apposed to the membrane motoneuron.
§
Percentage of the apposed bouton length detached from motoneuron membrane.
Number of sampled motoneurons, boutons or active zones is indicated in parentheses.