Abstract
The developmental expression of immunocytochemical reactivity to 3 monoclonal antibodies (Mabs Neu 4, Neu 5, and Neu 9) that were generated against adult rat olfactory epithelium was examined in olfactory tissues of embryonic rats. Tissues examined included the nasal olfactory epithelium, nerve, and olfactory bulb, as well as vomeronasal epithelium and nerve. Reactivity patterns of these Mabs in adult rats have been described previously (Hempstead and Morgan, 1985a). All 3 Mabs show reactivity on the cell surfaces of neurons, axons, and dendrites of the olfactory epithelium proper. Neu 5 alone shows reactivity on the dendritic knobs, site of transduction of the olfactory stimuli. These reactivities appear early, suggesting developmentally significant roles for the antigens to these Mabs. For Neu 5 and Neu 9 initial reactivity occurs on outgrowing olfactory axons at E13. Dendritic and perikaryal reactivities begin appearing at E14. For Neu 4 initial reactivity occurs simultaneously on olfactory neuronal perikarya, axons, and dendrites at E14. Reactivity also occurs on cells that migrate from the olfactory epithelium and are associated with the olfactory nerves. Within the developing olfactory bulb, Neu 5 behaves as a general cell-surface marker. Neu 4 and Neu 9, however, show enhanced reactivity in the glomerular layer after the onset of synaptogenesis. Reactivity is also seen in the nasal respiratory epithelium and in the vomeronasal epithelia and nerve. Neu 5 and several antibodies to rat neural cell adhesion molecules (N-CAMs) show similar, although not identical, immunohistochemical staining patterns. They also react with the same bands in Western blots of brain membrane preparations. Western blots of Neu 5-reactive material also show developmental and spatial correlations of apparent molecular-weight distributions expected of N-CAM-like components as well.