Fig. 6. Fgf8 is required for guidance of trochlear motor axons in vivo. (A) Diagram of explant culture. (B-G) MHB explants cultured for 48 hours and stained with F84.1 antibody. (B) Control explants cultured in the presence of DMSO alone. Note the formation of a single dorsal projection within the explant (C,D). Explant cultured in the presence of the FGFR inhibitor SU5402 at 10 µM; axons fail to navigate correctly within the explant. (E-G) Explants cultured in the presence of a neutralising anti-Fgf8 antiserum. Note that axonal misrouting occurs in both dorsal (arrow in E, arrowhead in F) and ventral (arrows in G) regions of explants. (F) Some appear to follow random or even circular trajectories within the explant (red arrowhead) around the bead. When axons did exit from the explant they did so over a wide region of its dorsal edge (E,G).