Figure 2. Correlations between asymmetric cAMP/cGMP elevation and the deviation angle of growth cones during free extension.

(a) Time-lapse fluorescence images of a freely extending growth cone co-expressing Epac1-camps and red cGES-DE5. The Roman numerals (i–v) indicate the time points shown in (b). (b) Time course of growth cone angle changes (see Methods). Right and left turns are defined as positive and negative values, respectively. The Roman numerals correspond those in (a). The orange horizontal line indicates the period when the maximum angle changes were calculated within 15 min after significant cAMP/cGMP_right/left elevation (asterisk). A significant elevation was defined as a change that was 2.58-fold more than the derivative of cAMP/cGMP_right/left and also cAMP/cGMP_left/right. The cyan line denotes the latency from a significant increase to the maximum angle change. (c) Spontaneous changes in the right/left ratios of cAMP/cGMP, cAMP, and cGMP (see Methods). (d) Cumulative distance during the observation of the growth cone in Fig. 2a. (e) Freely extending growth cones deviate toward the cAMP/cGMP elevated side. The maximum growth cone angle changes within 15 min after significant cAMP/cGMP elevation at the turning side were higher than in randomly selected cones (80 turnings from 14 growth cones). The randomly selected maximum growth cone angle changes were calculated as follows: select a time point from the overall time course and choose the maximum from within 15 min after the time point. Data are presented as means ± s.e.m. *P < 0.001.