Fig. 8: Ca²⁺ signaling in lumbar motoneurons in SCI mice after EEMS.

a Schematic of the fiber photometry setup. Ca²⁺ transients were recorded from motoneurons of freely moving mice. DM, dichroic mirror; PMT, photomultiplier tube. Schematic was created with BioRender.com. b Raw traces of changes in GCaMP6 fluorescence that were related to flexion of the ankle joint of the hind limbs. ΔF/F represents the change in fluorescence from the mean level before the task. c, e, g, i, k Ca²⁺ signals associated with ankle flexion in a single mouse from the sham (c), untrained (e), 10-Hz EEMS (g), 15-Hz EEMS (i), and 20-Hz EEMS (k) groups. Upper, heatmap of Ca²⁺ signals aligned with the initiation of ankle flexion. Each row plots one flexion event, and a total of six flexion events are illustrated. The color scale at the left indicates ΔF/F. Lower, plot of the average Ca²⁺ transients. Thick lines indicate the mean, and shaded areas indicate SEM. The red line indicates the time of ankle flexion. d, f, h, j, l Mean Ca²⁺ transients associated with ankle flexion for the entire test group (n = 5 mice per group) for each condition: sham (d), untrained (f), 10-Hz EEMS (h), 15-Hz EEMS (j), and 20-Hz EEMS (l). m Average peak fluorescence for six ankle flexions (n = 5 mice per group). The curve represents the mean of 30 signals, and the shaded areas indicate SEM. n The AUC of the average fluorescence peak for six ankle flexions (n = 5 mice per group). Data represent the mean ± SEM; ns: no statistically significant difference, *p < 0.05, **p < 0.01, ***p < 0.001, one-way ANOVA followed by the Bonferroni post hoc test.