Basic fibroblast growth factor and epidermal growth factor exert differential trophic effects on CNS neurons

Epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) are potent mitogenic proteins capable of inducing cell division in a wide variety of cell types. In addition to their mitogenic properties, both proteins have recently been shown to enhance survival and process outgrowth from neurons of central nervous system origin. The full spectrum of neuronal subtypes responding to these factors has not been elucidated. In the present study, EGF was found to enhance survival and process outgrowth of primary cultures of cerebellar neurons of neonatal rat brain. This effect was dose-dependent and was observed with EGF concentrations as low as 100 pg/ml. In marked contrast, bFGF was ineffective in enhancing survival or neurite elongation from cerebellar neurons when tested in the range of 0.1 to 10.0 ng/ml. However, within this concentration range, bFGF did prove effective in stimulating an increase in [3H]thymidine incorporation into primary cultures of cerebellar astrocytes, demonstrating that bFGF was active and that cells in the cerebellum do respond to bFGF. These results suggest that EGF or an EGF-like peptide may act as a neurite elongation and maintenance factor for cerebellar neurons. EGF has now been shown to support striatal, cortical, and cerebellar neurons, suggesting that this factor may have trophic activity throughout the central nervous system. bFGF, in contrast, appears to exert its effects on limited populations of neurons.