GFAP and Stroke: In contrast to 24 hours after irradiation, by 3 days after irradiation the astrocytes began exhibiting the classic GFAP+ reactive phenotype, which persisted for at least 7 days after irradiation (Figures 5A–C), resembling subacute and chronic astrocytic scarring that occurs on approximately the same timescale after CNS injury or stroke (29).