Epidermal growth factor exerts neuronotrophic effects on dopaminergic and GABAergic CNS neurons: comparison with basic fibroblast growth factor.

Basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) have been described to exert neuronotrophic effects on central nervous system neurons in culture. To study the selectivity of trophic actions of these growth factors, neurotransmitter-identified populations of embryonic rat mesencephalon were used. At 20 days in vitro, EGF (3 ng/ml) promoted survival and neurite outgrowth from these neurons. The neuritogenic effect of bFGF (3 ng/ml) was, however, more robust. Quantitative analysis with the neurofilament monoclonal antibody RR97 and ELISA confirmed the differential response, bFGF being 2-2.5 times more effective at all concentrations tested (ED100: 3-10 ng/ml for both EGF and bFGF). At 10 days in vitro, EGF displayed no trophic activity--even at 30 ng/ml. Treatment of mesencephalic cultures with EGF (3 ng/ml) for 20 days stimulated [3H]dopamine and [14C]GABA uptakes about 4-fold. While bFGF (3 ng/ml) also stimulated GABA uptake some 4-fold, dopamine uptake was increased almost 20-fold. Thus, EGF is also capable of enhancing the transmitter traits of selected central neuronal populations; however, the actions of bFGF appear to preferentially address dopaminergic cells.