TABLE 1.Motoneuron properties
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Neonate in Cultured Slices |
Embryonic in Primary Culture |
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Control |
G93A |
Control |
G93A |
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n | 23 | 16 | 27 | 40 | ||
Cell properties | ||||||
Soma diameter, µm | 32 ± 6 | 32 ± 4 | 27 ± 2 | 27 ± 3 | ||
Resting membrane.potential, mV | -52 ± 11 | -57 ± 11 | -70 ± 5 | -69 ± 6 | ||
Input resistance, MΩ | 52 ± 18 | 41 ± 24 | 360 ± 189 | 397 ± 237 | ||
Spike characteristics | ||||||
Duration, ms | 2.5 ± 1 | 2.4 ± 0.9 | 2.0 ± 0.5 | 1.9 ± 0.6 | ||
Amplitude, mV | 77 ± 14 | 71 ± 15 | 77 ± 7 | 72 ± 10* | ||
Threshold, mV | -45 ± 10 | -48 ± 5 | -49 ± 5 | -48 ± 5 | ||
f-I relation | ||||||
Slope, sp · s-1 · pA-1 | 0.25 ± 0.12 | 0.42 ± 0.14*** | 0.11 ± 0.05 | 0.16 ± 0.09** | ||
fmax, sp · s-1 | 95 ± 25 | 125 ± 29** | NM | NM | ||
I0, pA | 770 ± 640 | 580 ± 290 | 34 ± 44 | 26 ± 36 | ||
Post-spike AHP | ||||||
Amplitude, mV | 10 ± 2 | 10 ± 2 | 21 ± 5 | 20 ± 6 | ||
Post-train AHP | n = 11 | n = 11 | ||||
Amplitude, mV/spike | 0.6 ± 0.3 | 0.6 ± 0.3 | NM | NM | ||
Time constant, ms |
87 ± 19 |
84 ± 24 |
NM |
NM |
Comparison of properties of G93A and control motoneurons. Values are means ± SD. Neonatal (NC) neurons were held at -70 mV
by DC current clamp to prevent generation of action potentials by the spontaneous excitatory synaptic activity. Differences
between mean values were determined by t-test. Significance is indicated by *(P < 0.05), **(P < 0.005), and ***(P < 0.0005). The difference between the embryonic (EC) G93A and control spike amplitude is unlikely to affect the excitability,
as there was no correlation (r2 = 0.0001) between excitability (f-I slope) and spike amplitude. NM, not measured; AHP, afterhyperpolarization.