Figure 3.

Spatiotemporal Dynamics of Ca²⁺ in Growth Cones Responding to NGF Gradients

(A) Pseudo-color Ca²⁺ images in WT, R1KO, and R3KO growth cones 1 min before and 3.5 min after the onset of repetitive NGF ejection from the direction indicated by the white arrows. The growth cones were preloaded with a ratiometric pair of calcium indicators, OGB-1 and FR, and the OGB-1/FR emission ratio (F_OGB-1/F_FR, defined as R) was determined. Shown are relative changes in R (R/R_base, defined as R′) used as a measure of cytosolic Ca²⁺ levels. The near (red) and far (blue) ROIs were defined as described in Figure 2. Scale bar, 5 μm.

(B) Time course changes in R′ in the near (red line) and far (blue line) ROIs positioned on WT (dotted line), R1KO (finely dotted line), and R3KO (solid line) growth cones. Data from the first minute after the start of NGF ejection were excluded because of a lack of stable NGF gradients. Data are represented as mean ± SEM.

(C) The mean amplitude of R′ over the last 1 min of repetitive NGF ejection shown in (B). Each gray line connecting two dots represents data from the near and far ROIs of a single growth cone, and each colored bar represents the mean. ∗p < 0.05; ∗∗∗p < 0.001; ns, not significant; Wilcoxon matched pairs signed rank test.

See also Figure S2.