Figure 1. Induction of neurite formation in PC12 cells by nerve growth factor (NGF). PC12 cells were inoculated at 2×103 cells per microwell (0.32 cm2), and incubated for 2 days to allow complete cell attachment. Cells were then treated for 0 (day 0) or 3 days (day 3) with 50 ng/ml NGF. Aliquots of cells (day 3) were replenished with overlaying fresh NGF solution and incubated for another 2 days (day 5). Bar=100 μm.