Abstracts

Convulsive seizures increase brain glucose utilization as suggested by deoxyglucose studies and studies on endogenous or interstitial lactate levels. It is not well known whether seizure alters glucose availability or the balance between aerobic and anaerobic pathways. We used multiprobe microdialysis to study seizure-induced extracellular concentrations in glucose, lactate and pyruvate in brain and adipocyte tissue in freely-moving rats.
Under general anesthesia, a guide was placed stereotaxically to target a microdialysis probe into the striatum. One week later, striatal and subcutaneous probes were inserted under light volatile anesthesia. Five hours later, basal samples were obtained for one hour. The subjects were exposed to maximal electroshock (MES; 50 mA x 500 Hz x 0.3 sec) using earclip electrodes. Samples were obtained for an additional hour after the seizure.
MES increased signficantly glucose, lactate and pyruvate levels in both central and peripheral tissue over basal levels (P[lt]0.05). However, pyruvate and lactate increases in peripheral tissue were 5-10 fold more greater than in the brain (P[lt]0.05). In addition, a mild, but significant increase in lacate/pyruvate ratio was found in the adipocyte tissue (P[lt]0.05) but not in the brain.
In brain, glucose utilization increases after a convulsive seizures without metabolic evidence for hypoxia or ischemia. In peripheral tissue, pyruvate and lactate increases were disproportionately higher than in the periphery. This suggests brain mechanisms maintain a normal energetic balance during brief convulsive seizures despite marked seizure-induced disturbances of peripheral metabolism.
[Supported by: Southern Illinois University Central Research Committee]