Vascular perfusion and blood-brain glucose transport in acute and chronic hyperglycemia.

We studied the effects of acute and streptozotocin-induced chronic hyperglycemia on regional brain blood flow and perfusion characteristics, and on the regional transport of glucose across the blood-brain barrier in awake rats. We found (1) a generalized decrease in regional brain blood flow in both acute and chronic hyperglycemia; (2) that chronic, but not acute, hyperglycemia is associated with a marked and diffuse decrease in brain L-glucose space; and (3) that chronic hyperglycemia does not alter blood-to-brain glucose transport. Taken together, these results suggest that in streptozotocin-induced chronic hyperglycemia, there is a reduction in the proportion of perfused brain capillaries and/or an alteration in brain endothelial membrane properties resulting in decreased noncarrier diffusion of glucose.