ATP-SENSITIVE POTASSIUM CHANNELS AND LOCAL ENERGY DEMANDS IN THE RAT HIPPOCAMPUS - AN IN-VIVO STUDY

Microdialysis coupled with an enzyme-based flow injection analysis was used to monitor brain extracellular lactate and glucose in the freely moving rat. Glucose levels reflect the balance between supply from th e blood and local utilisation, and lactate eff lux indicates the degre e of local nonoxidative glucose metabolism. Local application of tolbu tamide, a blocker of the ATP-sensitive potassium channel, decreased ex tracellular glucose and lactate levels in the hippocampus but not in t he striatum. The increase in glucose and lactate levels following mild behavioural stimulation was also reduced by tolbutamide in the hippoc ampus. Similar effects on both basal and stimulated lactate levels wer e obtained with local application of 10 mM glucose. These results indi cate that ATP-sensitive potassium channels are active under physiologi cal conditions in the hippocampus and that the effects of tolbutamide can be mimicked by physiological glucose levels.