Cardiac sympathetic nerve activity during kainic acid-induced limbic cortical seizures in rats

We sought to define changes in cardiac sympathetic nerve activity that occur during seizures. We studied kainic acid-induced limbic cortical seizures in urethane-anesthetized rats using cardiac sympathetic nerve, blood pressure, and electrocardiography (ECG) recordings. We studied changes in ventilation rate before and during seizures. Cardiac sympathetic nerve activity was increased during limbic cortical seizures. The modest increases were similar to changes induced by nitroprusside infusion. The normal relation of cardiac sympathetic nerve activity to ventilation rate was lost during seizure activity. Changes in cardiac sympathetic nerve activity caused by changes in ventilation rate became unpredictable, and could be extreme. We conclude that the modest changes in cardiac sympathetic nerve activity contribute to the predominantly parasympathetic effects on the heart during limbic cortical seizures and periods of asphyxia. Further, ventilation rate changes might be associated with large sudden increases or decreases in cardiac sympathetic outflow during seizures.