DIFFERENTIAL EXPRESSION OF EXTRACELLULAR-MATRIX AND CELL-ADHESION MOLECULES IN THE OLFACTORY NERVE AND GLOMERULAR LAYERS OF ADULT RATS

Owing to the continual turnover of afferent input, the olfactory syste m offers a unique opportunity to study development and reorganization of neuronal networks in adults, To explore substrates that may underli e these processes in the adult olfactory system, we examined the expre ssion and distribution of extracellular matrix and cell adhesion molec ules (CAM) thought to be involved in axon guidance/extension. NCAM, la minin, and tenascin were all detected by immunocytochemistry in the ne rve and glomerular layers of the adult rat olfactory bulb, although th e intensity and laminar distribution were varied, Antisera for N-CAM(t otal), N-CAM(180), and tenascin bound to fascicles within the olfactor y nerve layer and the glomerular neuropil, However, binding was nonuni form in that only subsets of axon fascicles and restricted glomeruli s howed evidence of immunoreactivity, Antilaminin and a polyclonal antit enascin similarly exhibited heterogeneous intralaminar immunoreactivit y, Tenascin colocalized with glial processes at the borders of glomeru li and subcompartments of the glomerular neuropil, Laminin immuno-reac tivity was evident in subsets of olfactory nerve fascicles and, to a l esser extent, the glomeruli. The data are consistent,vith the notion t hat ongoing axon extension and glomerular targeting in the olfactory s ystem is subserved in part by a heterogeneous expression of the same e xtracellular matrix and CAMs present at higher levels during perinatal development, (C) 1998 John Wiley & Sons, Inc.