Exposure to hypoxia followed by re-oxygenation, or deliberate chemical damage (ablation), leads to the loss of neurons (orange) in red spotted newts, and also causes immune cells called microglia (grey) to proliferate. In ependymoglia stem cells (green), ROS are produced inside mitochondria and by NOX proteins at the cell membrane. Only NOX-derived ROS, which can be inhibited by the drug apocynin (bold red lines), are necessary for the proliferation of ependymoglia stem cells and the subsequent regeneration of lost neurons. Inhibiting the microglia with a drug called Dexamethasone (thin red lines) has no effect on the proliferation of the ependymoglia stem cells, which suggests that inflammation does not influence the regeneration of neurons. Bold black lines represent processes that are necessary for regeneration; the processes represented by thin black lines are not necessary for regeneration.