Fig. 4. In vitro neurotrophic effects of GDF-15/MIC-1. GDF-15/MIC-1 was assayed on rat midbrain DAergic neurons (A, B), rat serotonergic raphe neurons (C), and chick DRG neurons (D). A, Numbers of mesencephalic TH-positive neurons at DIV 7. C, No factors;BC, baculovirus control, i.e., noninfected cells;1, 2, 3, cultures treated with 0.01, 0.1, and 1 ng/ml GDF-15/MIC-1, respectively;G, GDNF (10 ng/ml). B, Numbers of mesencephalic TH-positive neurons at DIV 8, after intoxication with 100 μm Fe2+. C, No factors; NT-4 (10 ng/ml); GDF-15/MIC-1 (1 ng/ml). C, Numbers of TpOH and 5,7 DHT-positive cells at DIV 4 in cultures established from rat E14 raphe. C, Control; 1,2, Cultures treated with 5 (1) or 10 ng/ml (2) GDF-15/MIC-1. D, Numbers of chick (E8) DRG neurons at DIV 2. C, Control, 1, 2, 3, cultures treated with 1, 5, or 10 ng/ml GDF-15/MIC-1; G, cultures treated with GDNF (10 ng/ml); N, cultures treated with NGF (10 ng/ml). Data are given as means ± SEM (n = 3). All experiments were performed in triplicate and repeated at least three times. p values derived from Student's ttest are *p < 0.05, **p < 0.01, ***p < 0.001.