Fig. 4: NMDARs promote ETC growth via increasing ETC Ca²⁺ activities.

a Left, representative simultaneous time-lapse images showing evoked Ca²⁺ activity (top) and morphology (bottom) of an ETC. Right, traces of Ca²⁺ activities in the branch (top) and soma (bottom) of the ETC in responding to 405-nm laser-induced uncaging (dashed lines) of NP-EGTA/Ca²⁺ complex (dashed lines). T1 and T2 indicate the time points at which the images in (left) were captured. Scale bar, 10 μm. b Traces of Ca²⁺ activities in the branch (top) and soma (bottom) of an ETC in responding to 405-nm laser application (dashed lines) under DMSO condition as a control. c Summary data showing the comparison of evoked global Ca²⁺ transient frequency (x-axis) and growth rate (y-axis) of ETCs between NP-EGTA uncaging group and two control groups including DMSO and NP-EGTA sham uncaging (NP-EGTA sham). Each data point was obtained from individual larvae. d Positive correlation between the frequency of global Ca²⁺ transients and growth rate of ETCs. Black open dots indicate the data obtained from ETCs with various levels of spontaneous global Ca²⁺ activities (“Spont.”), and the pink, gray, and orange open dots represent the data shown in (c). The black line represents linear regression for all the data points. e Typical case from an ETC, showing Ca²⁺ activities under the three conditions. With MK-801 application, local Ca²⁺ transients in ETC soma or branches were still observed. Filled arrowheads, global Ca²⁺ transients; open arrowheads, local Ca²⁺ transients. f Summary data from 8 ETCs, showing the number of global Ca²⁺ transients per h in groups of Spont., Opto. stim., Opto. stim. + MK-801. Each data point was obtained from individual larvae. The number in the brackets indicates the number of ETCs. One-way ANOVA was used for c; two-sided Wilcoxon matched-pairs signed rank test was used for f; Simple Linear Regression analysis for was used for d. Data are represented as mean ± s.e.m.