Effects of Catecholamine Infusions on Cerebral Blood Flow and Oxygen Consumption of the Isolated Perfused Dog Brain

Our earlier studies revealed a weak alpha-adrenergic and beta-adrenergic activity of the cerebral vessels of the isolated perfused dog brain. The present investigations were undertaken to determine whether vascular adjustments occur in the cerebral circulation during longer periods of catecholamine infusions. The experiments were performed on six isolated canine brains cross perfused from donor dogs. Norepinephrine (2 µg per minute), epinephrine (2 µg per minute), and isoprenaline (0.2 µg per minute) were applied intra-arterially (i.a.) for a period of ten minutes. Total venous outflow, perfusion pressure in the circle of Willis, and venous O2 saturation were monitored continuously. Cerebral vascular resistance (CVR) and cerebral O2 consumption (CMRO2) were calculated. Based on the pressure-flow relationship tested in each brain, the indirect effects of catecholamines on CVR caused by autoregulatory influences were calculated and eliminated. During norepinephrine and epinephrine infusions cerebral blood f...