Brain development influences the appearance of glial factor-like activity in rat brain primary cultures

THE development of the nervous system in mammals is thought to be a complex process which involves the orderly expression of a pattern of signals and events. The understanding of how development is controlled requires the identification of the biochemical events which are causally related to this process. Established cultured cell lines provide useful model systems which have yet to be validated by careful examination in conditions more closely related to those in vivo. We have shown previously that established glial cell lines release a macromolecular factor(s) which can induce morphological differentiation of neuroblastoma cells1 and this glial factor(s) is distinct from the well characterised nerve growth factor2. Here we report that glial factor (GF) activity is not confined to established cell lines, as a similar activity is also detected in the medium conditioned by certain primary cultures of rat brain. We further demonstrate that there is a correlation between the presence of GF activity in the medium from cultures of various brain regions and the age of the animal at the autopsy from which the primary culture was derived. Our results provide experimental evidence that primary cultures initiated at different developmental stages can parallel the cellular and biochemical development of the brain in vivo.