Production and cell identification of peroxynitrite (ONOO-) in wild type (Wt) (upper) and gp91phox-/- (lower) mice 48 hours after TBI. ONOO- in Wt mice was produced in microglia-like cells (left, arrows), astrocytes (middle, arrows), and degenerated neurons (right, arrows). In gp91phox-/- mice, ONOO- production was strongly suppressed. In neurons, only weak production of ONOO- was observed, but degeneration of neurons was not seen (right, arrows). Scale bars = 20 μm.