Fig. 4.

EphrinA5 induces collapse of rostral raphe serotonin axons in vitro. A, Explant preparation: hindbrain was dissected as an open book from E12 embryos; the rostral and caudal raphe were dissected as depicted on a whole-mount E12 hindbrain stained for 5-HT. Scale bar = 2 mm. B, Raphe explants (3DIV) were stained for 5-HT (green) and phalloidin (red). B1, 5-HT⁺ axons emerging from the explant. B2–B5, 5-HT–labeled growth cones displaying either a normal fan-like morphology (B2, B3) or collapsed growth cone with branch-like morphology (B4) or a long trailing process and an actin-rich retraction bulb. Scale bar = 100 μm (B1), 10 μm (B2–B5). C–F, Histograms show the percentage of collapsed growth cones when explants are exposed to different concentrations of ephrinA5. C, D, 5-HT–labeled axons from rostral (C) and caudal (D) explants; E, F, non–5-HT axons from rostral (E) and caudal (F) explants (>5 explants and >100 growth cones per condition). Data are presented as mean ± SEM. One-way ANOVA, *p < 0.05, **p < 0.01, ***p < 0.005, and ****p < 0.001.