Selective Metabolic Activation of the Hippocampus during Lidocaine-Induced Pre-seizure Activity

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Abstract
Neurophysiologic studies indicate that local anesthetic-induced seizures are generated in subcortical brain structures. A quantitative autoradiographic technique was utilized to measure cerebral metabolism during lidocaine-induced seizure activity in rats anesthetized with nitrous oxide. Local cerebral metabolic rate for glucose (l-CMRg) was determined when lidocaine infusion resulted in sustained EEG patterns consisting of .apprx. 100-125 .mu.V discharges with a frequency of about 9 Hz, lasting 1-2 s and superimposed upon almost isoelectric periods lasting 1-3 s. Significant reductions in l-CMRg (30-70% decreases) occurred in 19 of 26 regions surveyed. All areas of cerebral cortex had decreased glucose uptake following lidocaine administration. The hippocampus developed a striking increase in l-CMRg of 237%, while the amygdala and other related nuclei sustained metabolic rates similar to those present before lidocaine was given. This study demonstrates a coupling of metabolic activity with functional activity in subcortical structures recognized to be involved in the generation of local anesthetic seizure activity. Additionally, it reveals a heterogeneous of cerebral metabolism to lidocaine infusion in the presence of subcortically localized seizures.