Figure 7.

Hydrogen peroxide exposure leads to irreversible axonal degeneration.A. Neurons were treated with 100 μM hydrogen peroxide for one hour, and then returned to control media immediately after exposure. Cell morphology remained normal right after the exposure. However, signs of axonal degeneration were noted within a few hours after treatment and most axons were completely degenerated by 24 h. Scale bar, 20 μm. B. The degree of axonal degeneration was scored basing on axonal morphology (Y-axis, right side) and cell death was assayed by staining of ethidium homodimer and rejection of calcein AM (Y-axis, left side). Axonal degeneration clearly preceded neuronal death. For control neurons, the degeneration score was less than 1 and the percentage of cell death was less than 10% even at 24 h after mock treatment. Degeneration scores are based on analysis of more than 90 regions and cell death analyses from counts of more than 300 cells in three independent experiments. Error bar indicates SD.