Cerebral ischemia leads to early stabilization of hypoxia-inducible factor 1α (HIF1α) and upregulation of sulfonylurea receptor 1 (SUR1) in cerebral microvessels. (A, B) Immunolabeling of the middle cerebral artery (MCA) territory of the rat brain for IgG (A) or SUR1 (B) 1 and 3 hours after reperfusion, following 105 minutes ischemia; the pattern of labeling showing elongated structures is consistent with early involvement of microvessels (B, left); regions sampled in panel B are indicated with arrows in panel A. (C, D) Magnified views of double labeling experiments showing expression of SUR1 (red) in microvessels at 1 hour, colabeled with von Willebrand factor (green) (C), or in neurons at 3 hours, colabeled with NeuN (green) (D); superimposed images are also shown, with nuclei labeled using 4′,6-diamidino-2-phenylindole (DAPI) (right-hand panels). (E) Immunolabeling of the MCA territory of the rat brain for HIF1α 15 minutes after onset of ischemia; the pattern of labeling showing elongated structures is consistent with early involvement of microvessels (right panel). The data shown are representative of five experiments each.