Increased angiogenesis and arteriogenesis in diabetic GK rats. A–D: Representative brain images of 10-week-old control (A and B, n = 9) and diabetic GK (C and D, n = 7) rats infused with Pu4ii indicate increased vascular tortuosity (corkscrew pattern) indicative of vascular remodeling and collateralization in diabetes. Arrow: collaterals between MCA and PCA or ACA; arrow head: anastomoses between MCA branches. E: Number of collaterals was significantly increased in 10-week-old GK rats compared with control but not in younger 5-week-old animals (n = 5 per group) before the onset of diabetes. In 10-week-old animals, the diameter of the collaterals (F), the anastomoses within the MCA tree (G), and the total microvessel density (H) were all increased in diabetes (n = 6 per group). *P < 0.05 vs. control. □, 5 weeks; ■, 10 weeks. (A high-quality color digital representation of this figure is available in the online issue.)