Fig. 4. PI3-kinase is involved in agrin-induced growth-cone turning of Xenopus neurons. (A) Microscopic images of cultured Xenopus spinal neurons (preincubated with different PI3-kinase inhibitors for 20 minutes) at the beginning (0 min) and the end (60 min) of a 1-hour exposure to an agrin gradient applied by a micropipette (100 µg/ml in the micropipette, arrows). Agrin (DMSO), Agrin (Wort) or Agrin (LY) depict neurons pretreated with DMSO as control, with wortmannin (100 nM) or with LY294002 (30 µM), respectively. (B) Left: histogram showing the average turning angles of growth cones from neurons. Each value represents the average±s.e.m.; ^*P<0.01 (Student's t-test). Scatter plots showing the distribution of turning angles of each growth cone. Right: histogram showing the average neurite extension rates during the 1-hour growth cone turning assay. Scatter plots show the distribution of the neurite extension rate of each neuron.