IMMUNOHISTOCHEMICAL CHANGES IN THE ANTERIOR OLFACTORY NUCLEUS OF THE DEVELOPING RAT

The anterior olfactory nucleus (AON) is located caudal to the olfactor y bulb in the olfactory peduncle. Although this important structure is involved in the bilateral coordination of olfactory information, rela tively little is known about its development, structure, or function. The present report details results from an immunohistochemical examina tion of specific neuronal (microtubule-associated protein-2: MAP2, cal bindin D28-k, neuropeptide-Y: NPY) and glial (astrocytes; glial fibril lary-associated protein, or GFAP, oligodendrocytes; RIP) populations i n postnatal Days 10, 20, and 30 rats. MAP2-immunoreactivity (-ir), was present throughout the AON, although most dense in the outer plexifor m layer. Increases in labeling occurred from Day 10 to Day 30, reflect ing the maturation of dendritic processes. Both temporal and regional differences in expression were found with the two neuronal markers. Fo r example, although substantial numbers of calbindin-ir cells were obs erved as early as Day 10, relatively few cells exhibited NPY-ir. An ap parent decline in the number of stained figures was observed from Days 20-30 with both markers. Most cells exhibiting calbindin- or NPY-ir w ere found in the inner half of the cellular zone of the AON. GFAP-ir w as localized mainly to the subependymal zone and the lateral olfactory tract (LOT) at Day 10, with successive increases in staining in the c ellular and plexiform layers at Days 20 and 30. Oligodendrocyte-ir was restricted to the anterior commissure a dn the LOT at Day 10, with dr amatic increases in labeling of the cellular and plexiform layers obse rved by Days 20 and 30. These results represent some of the first anal yses of the maturation of the first analyses of the maturation of spec ific cellular phenotypes within this large neural region. (C) 1997 Joh n Wiley & Sons, Inc.