Figure 2

Torpor does not affect neuronal structural integrity in mice. (A) Representative images of a Golgi-Cox stained CA1 pyramidal neuron at 10 × magnification (left), a tracing (green) and Scholl analysis (white) of the same neuron (middle; 1 soma radius = 10 µm) and a 40 × magnification used for spine counting (red arrows). (B) Scholl analysis revealed no significant differences in dendritic complexity between torpor phases (EU, PT, TL, AE and AL; n = 10 neurons per animal from 6 animals per group; Two-way ANOVA F_4,296 = 2.022, p = 0.0913). (C) Total dendritic length of CA1 pyramidal neurons did also not differ significantly between groups (One-way ANOVA F_4,295 = 2.244, p = 0.63). (D-E) Basal (D) and apical (E) spine count did not differ significantly between groups either (One-way ANOVA F_4,295 = 2.044, p = 0.22 and F_4,295 = 1.077, p = 0.37, respectively). (F-G) Cumulative frequency distributions (F) and geometric means (G) of basal spine head diameters did not reveal significant differences among groups (Kruskall-Wallis p = 0.90; One-way ANOVA F_4,2574 = 2.316, p = 0.055). (H-I) Cumulative frequency distributions (H) and geometric means (I) of apical spine head diameter revealed a significant decrease in spine head diameter at AE compared to EU in geometric means only (0.44 ± 0.01 µm vs 0.38 ± 0.010 µm; One-way ANOVA F_4,2863 = 5.346, p = 0.0015; post-hoc Tuckey p = 0.0016), not in frequency distribution (Kruskall-Wallis p = 0.92). Spine head diameter was restored again in AL.