Table 3.
Effects of Aging and Endurance Training on Neuromuscular Junction Morphology of EDL Muscles.
| Pre-synaptic | Young, Control | Young, Trained | Aged, Control | Aged, Trained |
|---|---|---|---|---|
| Branch number | 9.5 ± 1.0 | 11.3 ± 0.9 | 10.5 ± 0.8 | 9.1 ± 0.8 |
| Total branch length (µm) | 106.1 ± 11.6 | 112.9 ± 12.3 | 103.9 ± 8.1 | 97.5 ± 5.6 |
| Average branch length (µm) | 12.3 ± 0.8 | 11.0 ± 0.7 | 11.3 ± 0.9 | 12.3 ± 0.9 |
| Branching complexity | 12.9 ± 2.5 | 15.8 ± 2.9 | 14.3 ± 1.9 | 10.8 ± 1.6 |
| Vesicles stained area/Total branch length |
1.0 ± 0.1 | 0.9 ± 0.1 | 1.1 ± 0.1 | 1.0 ± 0.1 |
| Total vesicles perimeter (µm) | 126.2 ± 10.8 | 129.1 ± 10.8 | 129.2 ± 10.2 | 123.2 ± 3.6 |
| Stained vesicles perimeter (µm) | 208.5 ± 18.4 | 202.7 ± 25.9 | 207.6 ± 12.5 | 209.7 ± 18.2 |
| Total area vesicles (µm2) | 525.7 ± 72.6 | 520.2 ± 48.7 | 569.7 ± 39.7 | 537.5 ± 48.7 |
| Stained area vesicles (µm2) | 90.2 ± 15.4 | 89.2 ± 11.1 | 96.6 ± 9.1 | 92.7 ± 11.3 |
| Vesicle dispersion (%) | 21.0 ± 3.1 | 21.7 ± 3.5 | 20.5 ± 1.7 | 19.5 ± 1.6 |
| Post-synaptic | ||||
| Total receptors perimeter (µm) | 134.7 ± 9.5 | 133.2 ± 11.3 | 131.1 ± 8.7 | 125.0 ± 5.3 |
| Stained receptors perimeter (µm) | 257.2 ± 21.1 | 240.6 ± 25.9 | 252.6 ± 18.0 | 223.9 ± 16.7 |
| Total area receptors (µm2) | 659.6 ± 74.5 | 631.3 ± 86.7 | 637.5 ± 48.3 | 625.6 ± 52.0 |
| Stained area receptors (µm2) | 215.6 ± 23.1 | 220.7 ± 24.3 | 226.3 ± 20.3 | 212.4 ± 30.5 |
| Receptor dispersion (%) | 35.9 ± 2.6 | 38.8 ± 1.8 | 39.6 ± 2.4 | 38.3 ± 2.9 |
| Receptors stained area/Total branch length | 2.5 ± 0.4 | 2.2 ± 0.2 | 2.5 ± 0.2 | 2.4 ± 0.3 |
| Receptor/Vesicle coupling (%) | 50.7 ± 11.0 | 45.2 ± 6.1 | 48.1 ± 3.6 | 51.4 ± 3.4 |
Values are means ± SE, N=9/group.
Branching complexity = branch number x total branch length/100. Vesicle dispersion = stained area/total area x 100 (lower % indicates greater dispersion). Receptor dispersion = stained area/total area x 100 (lower % indicates greater dispersion). Receptor/Vesicle coupling = vesicle stained area/receptor stained area x 100 (higher % indicates greater degree of overlap between pre-synaptic vesicles and post-synaptic receptors).