Fig. 2.
Growth cone turning toward LN-coated beads requires an influx of extracellular Ca2+ and CaM activity. A deviation of the original course of advance >15° defined a positive growth cone turning response. Under control conditions, >75% of growth cones that were investigated respond positively. Blocking Ca2+ channels (2 mm each,Ni2+ andCo2+) or chelating extracellular Ca2+([EGTA]o) or intracellular Ca2+([AM-BAPTA]i) significantly reduces the number of growth cone turnings. Inhibition of CaM with 10 μm fluphenazine-2-N-chloroethane (FPC) blocks growth cone turning, whereas inhibition of CaM-kinase II (2 μmKN-62) is ineffective. None of the inhibitors tested altered growth cone advance on the FN substrate for the time period of observation. The significance of the effects of each inhibitor was compared with a parallel control (t test). Control value shown is an average of all controls. Error bars indicate SEM.