Quantitative Changes of Cerebral Neocortical Structure in Insulin-Treated Long-Term Streptozocin-lnduced Diabetes in Rats

The brains of rats with streptozocin-induced diabetes treated with a low-dose insulin regimen (1 IU/day) were studied with morphometric techniques. After 1 yr of diabetes, brain weight decreased slightly (1350 ± 71 vs. 1521 ± 55 mg, 2P < .01) as did the volume of the neocortex (498 ± 36 vs. 567 ± 40 mm³, 2P < .05). A significant loss of neocortical neurons occurred (38 ± 2 × 106 vs. 46 ± 3 × 10⁶, 2P < .01), and the length of the capillary network in the neocortical tissue shortened disproportionately (405 ± 102 vs. 631 ± 47 m, 2P < .01), leading to increased diffusion distance. The mechanisms underlying cerebral loss in this model are unknown, but abnormalities of the vascular supply with prolongation of the route of diffusion might play a role.