p75^NTR and NADE induction in neurons. A–F, Fluorescent photomicrographs of cortical cultures containing both neurons and astrocytes, immunocytochemically stained with anti-p75^NTR antibody (A), anti-NADE antibody (D), or anti-NeuN antibody (B,E) 4 hr after 15 min exposure to 300 μm zinc. p75^NTR and NADE immunoreactivity was visualized with rhodamine-labeled secondary antibody (red) and NeuN immunoreactivity (a specific marker for neurons) with FITC-labeled secondary antibody (green). Composite images ofA and B (C) andD and E (F) revealed that p75^NTR and NADE were expressed almost exclusively in neurons (yellow). Scale bar, 200 μm. G,H, Fluorescent photomicrographs of identical field of cortical culture 4 hr after 15 min exposure to 300 μm zinc, stained with anti-p75^NTRantibody (G) or anti-NADE antibody (H). Arrows denote same neurons. NADE expression appeared to occur in a subset of p75^NTR-expressing neurons. Scale bars, 200 μm.