DIFFERENTIAL TROPHIC EFFECTS OF BASIC FIBROBLAST GROWTH-FACTOR, INSULIN-LIKE GROWTH-FACTOR-I, AND NEUROTROPHIN-3 ON STRIATAL NEURONS IN CULTURE

We have examined the trophic effects of basic fibroblast growth factor (bFGF), truncated insulin-like growth factor-1 (tIGF), and neurotroph in-3 (NT-3) on embryonic striatal neurons grown under serum-free cultu re conditions, Striatal neurons were identified using immunocytochemis try for dopamine- and cyclic AMP-regulated phosphoprotein (DARPP-32). In our serum-free striatal cultures, the survival and the development of DARPP-32-containing neurons were dependent on initial plating densi ty: relatively high density cultures yielded disproportionately increa sed number of harvested DARPP-32-positive neurons. All three growth fa ctors, bFGF (10 ng/ml), tIGF-1 (50 ng/ml), and NT-3 (50 ng/ml), promot ed the survival of DARPP-32-positive neurons, with bFGF being signific antly more effective than tIGF-1 and NT-3. Exposure to bFGF also signi ficantly increased the total cell number compared to control cultures, whereas there was only a tendency toward more (20-30%) surviving cell s in cultures treated with either tIGF-1 or NT-3. With the concentrati ons used, only bFGF gave rise to a significant increase (80%) in the n umber of glial fibrillary acidic protein-immunopositive glia as compar ed to controls. The most pronounced effect on morphological developmen t of DARPP-32-containing neurons was seen with NT-3, which increased t he length of neurites, the number of branching points on the neurites, and the soma area. There was no alteration of the morphology of this neuronal population in bFG;F-treated cultures. All of these growth fac tors were seen to be approximately equally efficient at protecting str iatal neurons from N-methyl-D-aspartate-induced excitotoxicity. These data indicate that bFGF, tIGF-1, and NT-3 exert differential trophic a ctivities on striatal neurons in vitro and suggest that these growth f actors might also be involved in the regulation of neuronal developmen t and maintenance in the striatum. (C) 1996 Academic Press, Inc.