Figure 5.

R3KO Growth Cones Are Hypersensitive to IP₃-Based Guidance Signals

Shown are growth cone responses to lower doses of IP₃ (A–C) and NGF (D–F).

(A) Average turning angles of WT and R3KO growth cones 30 min after the onset of repetitive FLIP of a smaller amount of caged IP₃ (0.1 μM in contrast to 0.5 μM in Figure 1B). ∗p < 0.05; student's t test.

(B) Time course changes in F′, calculated as F/F_base of Fluo-8H fluorescence, in the near (red line) and far (blue line) ROIs positioned on WT (dotted line) and R3KO (solid line) growth cones in response to repetitive FLIP of a smaller amount of caged IP₃ (0.1 μM in contrast to 0.5 μM in Figure 2B).

(C) The mean amplitude of F′ over the last 30 s of repetitive FLIP shown in (B). ∗∗∗p < 0.001; ns, not significant; paired t test.

(D) Average turning angles of WT and R3KO growth cones 40 min after the start of repetitive ejection of NGF. In-pipette concentration of NGF was 0.4 μg/mL in contrast to 20 μg/mL in Figure 1D. ∗p < 0.05; student's t test.

(E) Time course changes in R′, calculated as R/R_base of a ratiometric pair of OGB-1 and FR, in the near (red line) and far (blue line) ROIs positioned on WT (dotted line) and R3KO (solid line) growth cones in response to NGF gradients. In-pipette concentration of NGF was 0.4 μg/mL NGF in contrast to 20 μg/mL in Figure 3B.

(F) The mean amplitude of R′ over the last 1 min of repetitive NGF ejection shown in (E). ∗∗p < 0.01; ns, not significant; Wilcoxon matched pairs signed rank test. In (A and D), bars represent mean ± SEM, with each gray dot indicating turning angle of individual growth cones in this experiment.

In (B and E), data are represented as mean ± SEM. In (C and F), 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.