CHANGES IN THE EXPRESSION OF THE EXTRACELLULAR-MATRIX MOLECULES TENASCIN-C AND TENASCIN-R AFTER 3-ACETYLPYRIDINE-INDUCED LESION OF THE OLIVOCEREBELLAR SYSTEM OF THE ADULT-RAT

In the central nervous system of rodents, the extracellular matrix gly coproteins tenascin-C and tenascin-R are expressed predominantly by as trocytes and oligodendrocytes respectively. Both molecules support neu rite outgrowth from several neuronal cell types when presented as unif orm substrates. When offered as a sharp boundary with a permissive sub strate, however, both molecules prevent neurite elongation. On the bas is of these observations it has been suggested that tenascin-C and ten ascin-R may be relevant in determining the cellular response after inj ury in the adult rodent central nervous system. To investigate whether tenascin-C and tenascin-R may play important functional roles in the lesioned central nervous system, we have analysed their expression in the olivocerebellar system of the adult rat after 3-acetylpyridine-ind uced degeneration of nerve cells in the inferior olivary nucleus. Tena scin-C mRNA was not detectable at any time in the unlesioned or lesion ed inferior olivary nucleus by in situ hybridization. In the cerebella r cortex, tenascin-C mRNA in Golgi epithelial cells was down-regulated 3 days after the lesion and returned to control values 80 days after the lesion. Tenascin-R mRNA was expressed by distinct neural cell type s in the unlesioned olivocerebellar system. After a lesion, the densit y of cells containing tenascin-R transcripts increased significantly i n the inferior olivary nucleus and in the white matter of the cerebell ar cortex. Immunohistochemical and immunochemical investigations confi rmed these observations at the protein level. Our data thus suggest di fferential functions of tenascin-C and tenascin-R in the injured centr al nervous system.