Secretion of GDNF by glial cells does not account for the neurotrophic effect of bFGF on dopamine neurons in vitro.

The neurotrophic effect of bFGF on dopamine (DA) neurons in vitro depends upon its mitogenic activity on glial cells. We examined whether glial secretion of the dopaminergic growth factor GDNF is responsible for the trophic activity of bFGF on mesencephalic DA neurons. When added with lower concentrations of bFGF, GDNF had an additive trophic effect, which disappeared at optimal bFGF concentrations. However, addition of GDNF-neutralizing antibodies could not modify the bFGF-induced survival and growth of DA neurons. These results indicate that although GDNF could be secreted by bFGF stimulated glia, its secretion alone does not account for the trophic effect of bFGF on mesencephalic DA neurons.