β1-integrin function is essential for MAG-induced axonal growth cone repulsion of hippocampal neurons. A-C, Growth cone turning in a gradient of MAG (150 μg/ml in the pipette). Sample images show the axons of P5 rat hippocampal neurons in the gradient for 30' on the left and axonal growth cones at the onset (0') and at the end (30') of the turning assay at a higher magnification. Scale bar: 20 μm. Right traces show sample trajectories of axons during the turning assay from 15 randomly selected neurons. Scale bar: 5 μm. D. Summary of growth cone turning angles under different conditions. Similar as in (A-C), growth cones were subjected a gradient of MAG-Fc, heat-inactivated (HI) MAG, wild-type (RGD) and mutant forms (KGE, RAD) of MAG-Fc, or native human Fc fragment. Pharmacological reagents were preincubated for 30 min and present throughout the turning assay with the following concentrations: echistatin (100 nM); Ha2/5 (1 μg/ml); Control IgM (1 μg/ml). Data represent mean ± s.e.m. Numbers associated with bars indicate the number of growth cones analyzed under each condition. "*" indicates significant difference (p < 0.01, ANOVA).