Fig. 5. (A) Double immunofluorescence micrographs showing the distributions of tyrosinated -tubulin (TUB-IA2) and of the p110 subunit of PI3K in hippocampal pyramidal neurons after 18 hours in culture (in the presence of 50 ng ml^–1 BDNF). Cells were incubated for 5 minutes in control medium (bottom) or with 10 nM IGF-1 (top and middle), permeabilized in microtubule-stabilizing conditions, and then fixed for antibody labeling. Note that stimulation with IGF-1 triggers the association of p110 with microtubules primarily in the distal axon (top) and the axonal growth cone (middle). Bar, 20 µm (top and bottom) and 5 µm (middle). (B) Double immunofluorescence micrographs showing the distribution of the p110 subunit of PI3K in hippocampal pyramidal neurons after 36 hours in culture (in the presence of 50 ng ml^–1 BDNF). Cells were incubated for 5 minutes in control medium (right) or with 10 nM IGF-1 (left), permeabilized in microtubule-stabilizing conditions, and then fixed for antibody labeling. Bar, 20 µm (top) and 5 µm (bottom). (C) Double immunofluorescence micrographs showing the distribution of p110 and F-actin at the growth cone of an hippocampal pyramidal cell culture for 18 hours in the presence of 50 ng ml^–1 BDNF and incubated for 5 minutes with 10 nM IGF-1. Note that most of p110 immunostaining does not co-localize with F-actin. Bar, 5 µm.