Hypoperfusion decreases ABCB1 protein levels in brain capillaries through GSK3β/β-catenin pathway. Western blot analysis using brain capillary extracts showing that 24 and 48 hours after 1VO, (A) ABCB1 protein levels are decreased, (B) occludin protein expression is unchanged, (C) β-catenin nuclear abundance is decreased, and (D) tyrosine phosphorylation (pY) of GSK3β is increased, in ipsilateral hemisphere. Data are means ± SEM (n = 6). C, contralateral non-hypoperfused brain capillaries; I, ipsilateral hypoperfused brain capillaries; 1 VO 24 H, one vessel occlusion for 24 hours; 1 VO 48 H, one vessel occlusion for 48 hours. **P < 0.01 / ****P < 0.0001 compared with contralateral 24 hours // ##P < 0.01 compared with contralateral 48 hours (One-way analysis of variance (ANOVA) followed by Tukey’s multiple comparisons test).