CNS WHITE-MATTER CAN BE ALTERED TO SUPPORT NEURONAL OUTGROWTH

Previous work has demonstrated that white matter in the adult mammalia n CNS inhibits cell adhesion and neurite outgrowth. This phenomenon ha s been investigated most recently by culturing neurons on cryostat sec tions of the adult CNS. Employing this same technique, we have found, in accord with others, that neurons seldom adhere to or grow on centra l nervous system white matter but will attach and grow on gray matter. In the experiments presented here, embryonic rat hippocampal neurons were grown on cryostat sections from the adult rat CNS, in the presenc e of brain derived glial cocultures. It was found that the white matte r in cryostat sections can be modified by interaction with medium cond itioned by brain-derived glial cells. Neurons plated on sections pretr eated by such media show significant increases in both attachment and neurite outgrowth. The activity contained in glial conditioned medium is likely complex in nature. While the majority of the activity can be eliminated by heat treatment and trypsinization, neural adhesion but not neurite initiation is affected by protease treatment. Therefore, c ell attachment and neurite outgrowth may be regulated by different fac tors in the conditioned media. (C) 1994 Wiley-Liss, Inc.