ACTIVATION-INDUCED RESETTING OF CEREBRAL OXYGEN AND GLUCOSE-UPTAKE INTHE RAT

In the clinical setting it has been shown that activation will increas e cerebral glucose uptake in excess of cerebral oxygen uptake. To stud y this phenomenon further, this study presents an experimental setup t hat enables precise determination of the ratio between cerebral uptake of glucose and oxygen in the awake rat. Global CBF was measured by th e Kety-Schmidt technique, and the ratio between cerebral uptake rates for oxygen, glucose, and lactate was calculated from cerebral arterial -venous differences. During baseline conditions, rats were kept in a c losed box designed to minimize interference. During baseline condition s CBF was 1.08 +/- 0.25 mL.g(-1).minute(-1), and the cerebral oxygen t o glucose uptake ratio was 5.5. Activation was induced by opening the sheltering box for 6 minutes. Activation increased CBF to 1.81 mL.g(-1 ).minute(-1). During activation cerebral glucose uptake increased disp roportionately to cerebral oxygen uptake, and the cerebral oxygen to g lucose uptake ratio was 4.2. The accumulated excess glucose uptake dur ing 6 minutes of activation amounted to 2.4 mu mol/g. Activation was t erminated by closure of the sheltering box. In the postactivation peri od, the cerebral oxygen to glucose uptake ratio rose to a maximum of 6 .4. This response is exactly opposite to the excess cerebral glucose u ptake observed during activation.