Induction of GDNF mRNA by melatonin in C17.2 NSCs. (A,B) Gel images of RT-PCR amplification of GDNF (643 bp) and GAPDH (237 bp). Lanes 1–4: Control, 0.05, 0.1, and 1 nM melatonin. M = markers. (C) Percentage values of GDNF/GAPDH optical density ratios as a function of melatonin treatment. Data shown are the means ± s.e.m. from 2 separate experiments. *p < 0.05 vs control.