Fig. 8
Action potential train-evoked Ca2+ transients are larger and faster in swellings than stalks. a Representative image outlines a calyx loaded with Fluo-4FF (50 μM; KD = 9.2 μM) and Alexa 594 (15 μM) and frame-scanned by a two-photon laser scanning microscope. Action potential (AP) trains (100–300 Hz, 200 ms) were elicited by current injection in current-clamp mode or afferent stimulation using bipolar electrode. Ca2+ transients were recorded in swellings (location 1, 2, 3; red) and stalk (location 4; black). Changes in [Ca2+] were expressed as ΔG/R (see Methods). b Bar graphs (mean ± SEM) summarize amplitude, 10–90% rise time, decay time (τdecay), and integral (amplitude × τdecay) of Ca2+ transients in swellings (red; n = 9/8) and stalks (black; n = 9/8) at 100–300 Hz stimulation frequencies. Two-way repeated measures ANOVA with Bonferroni post hoc analyses was used to test significance. Critical p values were corrected by the number (3) of comparisons (*p < 0.0166, ***p < 0.0003). See Supplementary Table 3. Scale bar: 2 μm (a)
