Article Figures & Data
Figures
- Fig. 1.
Raw data traces showing LG-S EPSPs recorded at maximal group I strength in MG motoneurons. Traces show EPSPs recorded with a single pulse at 0.5 Hz (a,b) and during an 18 Hz pulse train (five pulses repeated every 2 sec) (c, d) and a 167 Hz pulse train (32 pulses repeated every 2 sec) (e,f). EPSPs were recorded from comparable cells (see below) in untreated (a, c,e) and 3-d-axotomized (b,d, f) rats. Tracesare representative of the observed mean effects of short-term axotomy, increased EPSP amplitude (a vs b) and increased negative modulation at 18 and 167 Hz (c vsd and e vs f, respectively). a, c, e(Untreated), EPSP amplitude = 4.8 mV, motoneuron CV = 40 m/sec, rheobase = 2.9 nA, IR = 2.0 MΩ, AHP amplitude = 2.7 mV, and AHP half-decay time = 26.0 msec. b,d, f (3 d axotomy), EPSP amplitude = 9.3 mV, motoneuron CV = 33 m/sec, rheobase = 5.3 nA, IR = 3.9 MΩ,, AHP amplitude = 3.4 mV, and AHP half-decay time = 23.0 msec.
- Fig. 2.
a, Cumulative histogram showing the increase in EPSP amplitude across the entire population of cells.b, Cumulative histogram showing the leftward shift in modulation 3 d after LG-S axotomy.
- Fig. 3.
Scatterplot of heteronymous (LG-S) EPSP amplitude versus modulation (see Fig. 1e):
Open and filled arrows indicate mean values in untreated and axotomized rats, respectively. The linear correlation between amplitude and modulation was significant for both groups (r = −0.37; p = 0.02;n = 39; and r = −0.55;p < 0.001; n = 42; untreated and 3 d axotomy, respectively). - Fig. 4.
Cumulative histogram showing the relative change in EPSP amplitude 2 sec after the 167 Hz stimulation (2 sec post-train ratio) (a) and 100 msec after the 167 Hz stimulation (0.1 sec post-train ratio) (b). Means for both ratios were not significantly different between untreated and axotomized groups (see Results).
Tables
Untreated 3 d axotomy n Mean ± SE Range n Mean ± SE Range Conduction velocity (m/sec) 46 49.9 ± 1.2 28.9–62.5 45 48.3 ± 1.2 28.3–61.3 Action potential amplitude (mV) 46 79.3 ± 1.2 68.5–93.9 45 78.3 ± 0.9 68.5–92.9 Rheobase current (nA) 41 7.6 ± 0.80 2.1–24.0 38 8.2 ± 0.82 1.5–20.6 Input resistance (MΩ) 19 1.6 ± 0.22 0.40–4.1 28 1.8 ± 0.23 0.22–5.2 AHP amplitude (mV) 29 1.7 ± 0.21 0.28–3.9 34 1.9 ± 0.13 0.79–4.1 AHP decay (msec) 29 15.7 ± 1.1 5.6–31.7 34 15.9 ± 0.96 8.1–34.8 EPSP amplitude (mV)* 46 2.3 ± 0.19 0.25–5.7 45 3.9 ± 0.34 0.79–9.7 167 Hz modulation (%)* 39 −39.0 ± 4.0 −79.0–24.0 43 −53.0 ± 4.0 −96.0–3.0 18 Hz modulation ratio* 43 0.88 ± 0.03 0.46–1.4 42 0.79 ± 0.02 0.61–1.2 2 sec post-train ratio 39 1.0 ± 0.03 0.71–1.6 43 0.98 ± 0.02 0.61–1.4 0.1 sec post-train ratio 39 0.99 ± 0.04 0.65–1.7 43 0.91 ± 0.03 0.51–1.4 *Significant difference (p < 0.05) between untreated and 3 d axotomy value.
