Figure 3. Immunocytochemical characterization of PC12 terminals II: varicosity markers.
(A–I) Fluorescence images of hippocampal neuron growth cones, PC12 growth cones and PC12 varicones, immunolabeled with non-growth cone markers (white/green) and co-labeled with phalloidin (actin, red). Calpain (A–C) is a protease enriched at the neurite shaft in neurons (A) but not so in PC12 cells (B–C), where it localizes almost exclusively to varicosities (white arrow). Synaptophysin (D–F) is a presynaptic marker that is barely detected in young growing neurites in hippocampal neurons (D) but enriched at PC12 varicosities (arrow in F). Scale bar = 10 µm.