Effects of Noradrenaline on the Cerebral Blood Flow in the Dog

The cerebrovascular response to intravenous noradrenaline infusion was studied in anaesthetized dogs during different and carefully controlled blood gas and arterial blood pressure conditions, using the radioactive gas elimination technique with external γ-registration. A flow reduction was found both at normocapnia and hypercapnia. Furthermore, in arterial hypoxia, which had induced vasodilatation a corresponding vasoconstriction was found. The response could be blocked by the α-adrenergic blocking agent phentolamine. Autoregulation of cerebral blood flow was found to function well during the influence of noradrenaline as well as after adrenergic α-receptor blocking by phentolamine.