REGIONAL DIFFERENCES IN GLIAL-DERIVED FACTORS THAT PROMOTE DENDRITIC OUTGROWTH FROM MOUSE CORTICAL-NEURONS IN-VITRO

To determine whether glia from different CNS regions differ in their a bility to support axons or dendrites, embryonic (E18) mouse cortical n eurons were cocultured with early postnatal (P4) rat astroglial derive d from cortex, retina, olfactory bulb, mesencephalon, striatum, and sp inal cord. After 5 d in vitro, axon and dendrite outgrowth from isolat ed neurons was quantified with double-labeling immunohistochemical tec hniques. Whereas axonal growth was similar an the various monolayers, total primary dendritic outgrowth was nearly threefold greater on glia derived from the cortex, retina, and olfactory bulb than on glia deri ved from mesencephalon, striatum, or spinal cord. This effect was prin cipally on the number of primary dendrites rather than the elongation of individual dendrites. Similar morphological differences were observ ed when cortical neurons were grown on polylysine in a noncontact cocu lture system with glia continuously conditioning the media. This selec tive promotion of dendrite growth was independent of neuron survival. These results indicate that there are regional differences in the abil ity of CNS glia to support dendritic growth and that this effect is du e, in part, to release of a diffusable factor.