GFAP and ischemia: The exercise-induced increase in the population of GFAP-positive astrocytes born between POD0 and 3 without increasing the total number of GFAP-positive astrocytes may be explained by promoting the decrease of GFAP expression in residential astrocytes before ischemia and inhibiting the decrease of GFAP expression in astrocytes born between POD0 and 3.