Repeatable focal seizure suppression: A rat preparation to study consequences of seizure activity based on urethane anesthesia and reversible carotid artery occlusion

Seizures can be associated with serious systemic complications (even death) due to autonomic nervous system or respiratory dysfunction. Clinical and laboratory studies examining the relationship between seizures and autonomic dysfunction have not resolved important questions, such as whether autonomic changes result primarily from muscle activation or from limbic cortical seizure activity, because correlational studies are limited by opportunities to observe seizures and study seizure spread. We describe a rat preparation that will greatly facilitate such studies. First, we show that systemic kainic acid in urethane anesthetized animals causes a period of status epilepticus as it does in ketamine/xylazine anesthetized or awake animals, but with a critical distinction: limbic cortical seizures occur without neocortical involvement. No paralytic agents are necessary to keep animals "safely" in a stereotaxic frame because there are not motor convulsions, yet animals continue to breathe on their own. Second, we describe the construction of a simple device to permit remote reversible unilateral or bilateral common carotid artery occlusion, and show that seizure activity in dorsal hippocampal regions can be unilaterally or bilaterally suppressed during periods of occlusion. Using this preparation, we found an increase in vagus nerve activity and a decrease in mean arterial pressure during suppression of right dorsal hippocampal seizures. By contrast, suppression of left dorsal hippocampal seizures caused no changes in vagus nerve activity and a small increase in mean arterial pressure. This preparation will be invaluable for defining the dynamic interactions of limbic brain regions and the interactions of limbic brain regions with autonomic brain regions.