1586 EFFECTS OF DOPAMINE ON CEREBRAL BLOOD FLOW (CBF) AND OXYGEN METABOLISM (CMRO₂) IN DOGS UNDER THE INFLUENCE OF E COLI ENDOTOXIN (ET)

Abstract

In normocapnic dogs ET causes a decreased CBF, an increased CMRO₂ and decreased cardiac output (CO) and mean aortic pressure (MAP). With a defective blood-brain barrier during endotoxemia a direct influence of monoamines on the cerebral metabolism is possible. Dopamine (DA), a neurotransmittor, was used to test this hypothesis.

In four dogs ET 1.0-1.5 mg/kg was injected over five minutes. CO and MAP were followed. CBF was measured using a radioactive gas elimination method (Xenon¹³³). CMRO₂ was calculated from CBF and the arteriovenous oxygen difference. Venous blood was sampled from the superior sagittal sinus. During the established shock phase dopamine HCl 10μg/kg min was infused. Effects after ET and ET+DA are compared.

The same dose of DA without ET causes an increased CBF without affecting CMRO₂. These results indicate a direct effect of DA on cerebral metabolism. The effects of ET can thus be influenced by treatments that normally would not affect the brain metabolism.

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