Fig. 3
Soma size contributes to an increased input resistance in induced mice. A Representative confocal images of gastrocnemius motoneurones (green) and soleus motoneurones (cyan) retrogradely traced using the Cholera Toxin β subunit conjugated to Alexa 488 (CTβ−488) and Fast Blue, respectively. B Scatter dot plots showing the 2D Soma size measurements for gastrocnemius motoneurones from the four different groups. This shows that the soma size decreased significantly in the induced mice compared to both the not-induced bigenic mice and tTa only controls, but returned to control (tTA only) values upon resuppression. Plot shows medians and interquartile ranges and each dot shows a single neurone. Medians (and IQR), Not-induced: 861.4 μm2(340.2), Induced: 507.6 μm2 (239.6), Resuppressed: 687.7 μm2 (317.6), tTA control: 687.1 μm2 (288,2). Kruskal Wallis, P <0.0001, Not-induced: n = 208 cells (8 mice, 4 female 4 male), Induced: n= 181 (8 mice, 5 female, 3 male), Resuppressed: n= 57 cells (4 mice, 2 female, 2 male) and tTA control: n=95 cells (6 mice, 3 female, 3 male). Dunn’s Multiple comparisons tests: Not-induced vs. Induced P <0.0001, Not-induced vs. resuppressed P <0.0001, Induced vs. resuppressed P <0.001, Not-induced vs tTA P <0.0001, induced vs tTA P <0.0001. Other pairwise comparisons were not significant. C Scatter dot plots showing the 2D Soma size measurements for soleus from the four different groups. This shows that the soma size for these cells decreased significantly in the induced mice compared to both the not-induced bigenic mice and tTA only controls, but returned to control (tTA only) values upon resuppression. Plot shows means and standard deviations and each dot shows a single neurone. Mean (and SD), Not-induced: 738.2 μm2 (227.9), Induced: 549.9 μm2 (171.5), Resuppressed: 634.3 μm2 (176.6), tTA control: 625.2 μm2 (209.5). ANOVA, P <0.0001, Not-induced: n = 67 cells (8 mice, 4 female, 4 male), Induced: n= 102 (7 mice, 4 female, 3 male), Resuppressed: n= 32 cells (6 mice, 3 female, 3 male) and tTA control: n=33 cells (4 mice, 3 female, 1 male). Tukey’s Multiple comparisons tests: Not-induced vs. Induced P <0.0001, Not-induced vs tTA P <0.05. Other pairwise comparisons were not significant. D Representative examples of the voltage drop in response to −3nA hyperpolarising current pulses to test input resistance. E Scatter dot plot showing input resistance from the four different groups. The input resistance increased significantly in the induced mice compared to both the not-induced bigenic mice and the tTA only controls, and returned to both control values upon resuppression. Plot shows medians and interquartile ranges and each dot shows the input resistance of a single neurone. Kruskal Wallis, P <0.0001. Medians (and IQR), Not-induced: 4.85 MΩ (3.04), Induced: 7.78 MΩ (2.92), Resuppressed: 4.45 MΩ (2.42), tTA control: 4.63 MΩ (2.29). Kruskal Wallis, P <0.0001, Not-induced: n = 74 cells (6 mice, 3 female, 3 male), Induced: n= 39 (9 mice, 5 female, 4 male), Resuppressed: n= 72 cells (6 mice, 3 female, 3 male) and tTA control: n= 56 cells (5 mice, 3 female, 2 male). Dunn’s Multiple comparisons tests: Not-induced vs. Induced P <0.0001, Induced vs. resuppressed P <0.0001, Induced vs tTA P <0.0001. Other pairwise comparisons were not significant. F Scatter dot plot showing the absolute sag for the four different groups. This suggests that the increased voltage drop in induced mice activate more Ih current. Plot shows medians and interquartile ranges and each dot shows the input resistance of a single neurone. Kruskal Wallis, P=0.0088. Medians (and IQR), Not-induced: 0.66mV (0.83), Induced: 1.29 mV (1.37), Resuppressed: 0.94 mV (1.17), tTA control: 0.98 mV (1.13). Kruskal Wallis, P <0.0001, Not-induced: n = 74 cells (6 mice, 3 female, 3 male), Induced: n= 39 (9 mice, 5 female, 4 male), Resuppressed: n= 72 cells (6 mice, 3 female, 3 male) and tTA control: n= 56 cells (5 mice, 3 female, 2 male). Dunn’s Multiple comparisons tests: Not-induced vs. Induced P <0.05. Other pairwise comparisons were not significant. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001