Table 1.
Changes of electrical properties of lumbar motoneurons with age in postnatal mice.
| P3–P5 | P8–P9 | ||
|---|---|---|---|
| Em (mV) | −68.89 ± 1.02 (19) | −70.03 ± 1.23 (34) | ns |
| Rin (MΩ) | 19.36 ± 1.42 (19) | 16.2 ± 0.82 (34) | * |
| Anti AP latency (ms) | 2.40 ± 0.29 (13) | 1.18 ± 0.13 (24) | *** |
| Anti AP amplitude (mV) | 77.9 ± 1.71 (13) | 82.98 ± 2 (24) | ns |
| Anti AP time to Peak (ms) | 1.39 ± 0.13 | 1.25 ± 0.06 (24) | ns |
| Anti AP half-width (ms) | 1.37 ± 0.08 | 1.08 ± 0.04 (24) | ** |
| Rheobase (nA) | 0.87 ± 0.11 (19) | 1.76 ± 0.2 (31) | ** |
| AP threshold (mV) | −50.2 ± 1.73 (9) | −47.88 ± 1.24 (26) | ns |
| AP amplitude (mV) | 62.08 ± 1.68 (12) | 68.11 ± 1.76 (11) | * |
| Time to peak (ms) | 1.19 ± 0.07 (12) | 0.99 ± 0.05 (11) | ns |
| Half-width (ms) | 1.28 ± 0.11 (12) | 0.97 ± 0.03 (11) | ** |
| AP Max depol | 123 ± 8.69 (12) | 149 ± 7.38 (11) | * |
| slope (mV/ms) | |||
| AP Max repol | −54.81 ± 5.34 (12) | −72.12 ± 2.90 (11) | ** |
| slope (mV/ms) | |||
| Gain (Hz/nA) | 23.80 ± 2.05 (13) | 25.63 ± 1.60 (11) | ns |
| AHP duration (ms) | 93.27 ± 7.40 (8) | 96.63 ± 6.61 (11) | ns |
| AHP amplitude (mV) | 5.01 ± 0.72 (8) | 5.26 ± 0.50 (11) | ns |
| AHP time max | 13.90 ± 1.94 (8) | 10.00 ± 1.37 (11) | ns |
| amplitude (ms) | |||
| AHP 1/2 duration (ms) | 47.10 ± 4.33 (8) | 36.78 ± 3.01 (11) | * |
| AHP decay time (ms) | 79.61 ± 8.27 (8) | 82.74 ± 5.40 (11) | ns |
| AHP 1/2 decay time (ms) | 34.16 ± 3.50 (8) | 27.78 ± 2.01 (11) | * |
P3–P5, postnatal days 3–5; P8–P9, postnatal days 8 and 9; Em, resting membrane potential; Rin, Input resistance, anti AP, antidromic action potential, latency, latency of AP elicited by electrical stimulation of the L5 ventral root; Time to peak, time needed for potential to rise from spike threshold to maximum value. Half width, time spent by the potential >50% of the maximum amplitude of action potential; Rheobase, lowest intensity of current injected through the electrode to elicit an action potential; AP threshold, voltage threshold measured at the foot of the action potential evoked by intracellular current injection; AP amplitude, amplitude of action potential measured between the foot and the peak; time to peak, measured as the time needed for the potential to reach the peak; Max depol slope, maximum slope of the depolarizing phase of action potential; Max repol slope, maximum slope of the repolarizing phase of action potential; Gain, slope of the steady state frequency-intensity curves measured during injection of long-duration pulse currents (800 ms to 1 s. AHP, Afterhyperpolarization, half duration of AHP is significantly shortened with age as well as half decay time. All values are means ± sem. The number of motoneurons is indicated between brackets after each mean value and sem. ns, non-significant difference; *p < 0.05, **p < 0.01; ***p < 0.005. Nonparametric permutation exact test.