1. Cerebral blood flow, oxygen and glucose consumption, hind-limb blood flow and oxygen consumption, blood pressure and heart rate were measured in seven ventilated dogs.
2. Inhalation of 5% CO2 caused a significant increase in cerebral blood flow and a significant decrease in cerebral glucose utilization.
3. Isoprenaline infusion (0·4 μg kg−1 min−1) caused a rise in cerebral blood flow, oxygen and glucose consumption. There was also an increase in peripheral blood flow and in most instances an increase in peripheral oxygen utilization.
4. The inhalation of 5% CO2 during isoprenaline infusion abolished the increase in cerebral blood flow, in cerebral glucose consumption and heart rate. Cerebral oxygen consumption was significantly decreased to below control values. Once the administration of 5% CO2 was discontinued an increase in peripheral oxygen consumption became apparent.
5. The possible therapeutic implications of these findings are outlined.