Neurite outgrowth and neurotoxicity of DRG neurons. (A) Neurite outgrowth of DRG neurons by NGF and GDNF. L4–L6 DRGs were harvested from naive or axotomized (AX) wild-type and Y1472F-KI mice at 4–5 weeks of age. DRG neurons were grown in the presence or absence of NGF (10 ng/ml) or GDNF (10, 50 or 100 ng/ml) for 22–26 h. Neurite outgrowth, shown in the photo, is presented as a percentage of total DRG cells. Data are presented as the mean ± SD (n = 3, 4, and 2 for NGF, GDNF, and axotomy, respectively). *P < 0.05 (two-tailed Student's t-test). (B) Neurotoxicity of glutamate toward DRG neurons. DRG neurons prepared from naive wild-type and Y1472F-KI mice were incubated without or with the indicated concentrations of glutamate for 24 h. The release of LDH was measured as described in the Methods section. Experiments (n = 5–6 at each concentration) were carried out by using 3 independent preparations. Data are presented as the mean ± SD of 3 experiments. *P < 0.05 vs. Y1472F-KI mice (two-tailed Student's t-test).