THE CEREBRAL-CORTEX ORIGIN OF ENFLURANE-INDUCED GENERALIZED SEIZURE IN CATS

The role of sensorimotor cortex (anterior and posterior sigmoid gyri) as the origin of enflurane-induced generalized seizures was examined a nd compared to that of lidocaine-induced seizures in cats. The inhaled enflurane concentration was adjusted at 3.5% in oxygen, the maximum p otency to induce generalized seizures. Repetitive electrical stimulati on with supramaximum intensity at a forepaw (2 Hz, 0.5 ms, 10 V) induc ed generalized seizures, which ended with a sudden appearance of isoel ectricity in the electroencephalogram (EEG), the so-called ''postictal depression.'' Repetitive auditory stimuli also induced similar grand mal-type EEGs.Unilateral ablation of the sensorimotor cortex completel y blocked the induction of generalized seizures by contralateral somat osensory stimuli. However, it had little effect on the induction of se izures by ipsilateral somatosensory stimuli or bilateral auditory stim uli. In contrast, bilateral ablation of the sensorimotor cortex did no t have a significant effect on the lidocaine-induced seizures. These f indings indicate that the involvement of the sensorimotor cortex is es sential for the development of enflurane-induced but not lidocaine-ind uced seizures.