MEMBRANE LIPID DEGRADATION IS RELATED TO INTERICTAL CORTICAL ACTIVITYIN A SERIES OF SEIZURES

Brain levels of free fatty acids (FFA) and diacylglycerols (DAG) rise rapidly with the onset of seizures, reflecting activation of phospholi pases A(2)(PLA(2)) and C (PLC), respectively. However, the ictal/inter ictal accumulation of FFA attenuates as recurrent seizures continue. T o assess the role of neuronal activity in stimulating PLA(2) and C, we compared FFA and DAG in rat cerebral cortex during recurrent ictal pe riods as a function of associated levels of interictal activity. Pento barbital -anesthetized rats were paralyzed, ventilated with 30% O-2 an d subjected to periodic pentylenetetrazol seizures at intervals of 5 m in. Animals were killed with focused-microwave irradiation during eith er the 3rd or 15th seizure. The rise in cortical FFA levels during ear ly seizures for 20:4, 22:6, and 18:0 was 3.6-, 2.5-, and 2.2-fold grea ter, respectively, when adjacent interictal activity was intense as co mpared to weak activity. During late seizures, this difference dropped to 2.2-fold for 20:4, the only FFA that showed a significantly higher value between robust versus weak interictal activity. In contrast, ac cumulation of DAG during early and late seizures was observed only whe n adjacent interictal activity was high. These results indicate that t he cortical accumulation of FFA and DAG during ictal periods of simila r intensity and duration depends upon the electrocortical activity dur ing adjacent interictal periods.