Figure 3

Early Growth Cone Collapse Can Be Dissociated From Long Term Axonal Fragmentation. (a) Scheme of treatments. After being in the presence of NGF for 3 days to allow axon growth, media is changed containing NGF (a1) or subjected to trophic factor withdrawal (a2), and fixed 24 hours later. To evaluate the reversibility of growth cone collapse, explants were subjected to TFW for 6 hours and then changed to a media with NGF and fixed 18 hours later (a3). Panels c, d, e and g use this letter-code for experimental treatments. (b,c) Representative images (b) and quantification (c) of the axonal area of control, deprived and NGF-rescued explants as specified in panel (a). Scale bar: 100 μm. (d) The proportion of growth cones in axonal tips is back to normal values in NGF-rescued axons. (e) NGF-rescued explants have larger axons than NGF-maintained explants. (f,g) Terminal branches (bifurcations close to the tip of axons, arrows in (f) are rare in control explants, but strikingly abundant in the rescued condition. Scale bar: 100 μm. (h,i) Representative images (h) and quantification of unfragmented axons (i) of control or 24-hours deprived explants in the absence or presence of taxol (10 μM). Scale bar: 100 μm. (j) Growth cone collapse induced by 3 hours of TFW is worsened in the presence of taxol (10 μM). Data are represented as mean ± SEM. (k,l) Axonal fragmentation induced by 6 hours of WD is significantly prevented by taxol 10 μM. Representative images (k) and quantification of unfragmented axons (l). Scale bar: 25 μm. (m) Growth cone collapse induced by 3 hours of WD is worsened in the presence taxol 10 μM. Data are represented as mean ± SEM.