Impaired beta-adrenergic mediated cerebral blood flow response in streptozotocin diabetic rats

The influence of intracarotic infusion of isoproterenol on cerebral blood flow, on cerebrovascular CO2-reactivity, and on cerebral glucose metabolism were investigated in streptozotocin diabetic rats. Resting cerebral blood flow in diabetic rats decreased by 26% from a control value of 90 ml/100 g.min. to 66 ml/100 g.min. Intracarotid isoproterenol infusion leads to a significant increase in cerebral blood flow in both groups. The increase in cerebral blood flow in control rats (70%), significantly exceeded that in the streptozotocin diabetic rats (33%). Cerebrovascular reactivity to carbon dioxide was preserved after isoproterenol infusion in both groups and there was no significant difference in the relative cerebral blood flow increase in the two groups. Cerebral glucose metabolism was also unaffected by the isoproterenol infusion. The results indicate that impaired beta-adrenergic mechanisms may play a role for alterations in cerebral blood flow that is seen in diabetes mellitus.