GFAP expression in hippocampi of aged female mice detected by immunohistochemistry. GFAP positive cells were shown as dark brown in color. Seven days after KA treatment, the intensity of GFAP staining in IL-18 KO mice (B) was similar to that in WT mice (A) with similar neuropathological changes. Very few reactive astrocytes were found in the hippocampi of saline-treated mice (C) and negative controls, with omission of the primary antibody, showed no positive staining (D). Bars = 100 μm.