P75NTR expression in the lesioned olfactory bulb: Olfactory bulb sections from sham and NMDA lesioned animals that were either estrogen or control-pellet replaced were probed for p75NTR expression and counter-stained with a nuclear dye (DAPI). A low magnification photomontage of olfactory bulb illuminated for DAPI is shown in (a). P75NTR is normally expressed in the glomerular layer of the olfactory bulb (b), photographed from the region indicated by the solid line box in (a). P75NTR is poorly expressed in other regions of the olfactory bulb, an example of which is shown in (c), taken from the region indicated by the wire frame in (a). However, in a comparable region of the NMDA-lesioned animals, diffuse p75NTR staining is seen in cells and fibers at the injury site (d). In estrogen-treated, lesioned animals p75NTR immunoreactivity is seen in cells associated with the walls of microvessels (e; g), identified by their curved nuclei (f; h) surrounding a lumen. Arrows indicate the same cells photgraphed under fluorescein (p75NTR; e,g) or UV illumination (DAPI nuclear dye; f,h). A double-labeled cell photographed under both fluoresein and UV is shown in (i). P75NTR labeling was not seen in microvessel walls in lesioned animals that received a control pellet (j) or in sections from estrogen-replaced lesioned animals that were incubated without a primary antibody (immunohistochemical control, l). Corresponding nuclear dye images are in k and m. Magnification bar: b-d = 160 μm; e-m = 25 μm.