Figure 4

Activity-dependent calcium signals in dendrites are reduced by stol^RNAi and stj^RNAi, whereas axonal ones are reduced by stj^RNAi but increases by stol^RNAi. (A) Pupal MN5 with targeted expression of GCaMP6s. Regions of interest in dendrites and in the axon (inset, upper right corner) are indicated by arrows and white circles. (B–Di) Changes in GCaMP6s fluorescence (ΔF/F) in dendrites (B, D) and in the axon (Bi, Di) upon induced firing by somatic ramp current injection as shown in (C). (B) As compared to control (white circles, n = 16) dendritic Ca²⁺ signals are significantly reduced by stj^RNAi (light gray circles; **p = 0.001, n = 11), stol^RNAi (dark gray circles; ***p < 0.001, n = 26), and stj^RNAistol^RNAi (medium gray circles; ***p < 0.001, n = 28), with no significant differences between both single- and the double knock-down. (Bi) By contrast, axonal Ca²⁺ signals are significantly reduced by stj^RNAi (light gray circles; ***p < 0.001, n = 15) but significantly increased following stol^RNAi (**p = 0.001, N = 11) as compared to control (Bi, N = 19). stj^RNAistol^RNAi (medium gray circles, N = 15) also significantly reduces axonal Ca²⁺ signals, but significantly less than single stj^RNAi (*p = 0.03). Data in (B and Bi) are presented as single data points and median. Statistical significance was tested by Kruskal–Wallis ANOVA with Dunn’s post-hoc test. (D–Di) Representative traces of (ΔF/F) over time in dendrites (D) and in the axon (Di) for control (black), stj^RNAi (light gray), stol^RNAi (dark gray), and stj^RNAistol^RNAi (medium gray).