Fig. 2.

The response of cortical axons toward semaphorins depends on their spatial distribution. a, Growth on gradients. The length of cortical axons growing on gradients of control membranes or membranes containing Sema3A or Sema3C was determined separately for those growing uphill (filled bars) or downhill (open bars) gradients (n is number of explants; Student's unpaired t test; **p < 0.001; ns, not significant).b, Growth on homogeneous substrates. Eachdot corresponds to the mean axonal length measured for different explants on uniform substrates of control membranes (open squares), Sema3C-containing membranes (filled triangles), or Sema3A-containing membranes (filled circles). The reduction of axonal length was strongly correlated with the concentration of Sema3A, whereas decrease of fiber length induced by Sema3C was independent of its concentration.