Repeated amygdala-kindled seizures induce ictal rebound tachycardia in rats

Abstract

It is thought that cardiovascular changes may contribute to sudden death in patients with epilepsy. To examine cardiovascular alterations that occur during epileptogenesis, we measured the heart rate of rats submitted to the electrical amygdala kindling model. Heart rate was recorded before, during, and after the induced seizures. Resting heart rate was increased in stages 1, 3, and 5 as compared with the unstimulated control condition. In the initial one third of the seizures, we observed bradycardia, which increased in intensity with increasing stage and was blocked by injecting methyl atropine. During stage 5 seizures, a rebound tachycardia was observed that also increased in intensity with increasing number of seizures. This study demonstrated the influence of seizure frequency on cardiac autonomic modulation, providing a basis for discussion of potential mechanisms that cause patients with epilepsy to die suddenly.

The Insular Cortex and the Regulation of Cardiac Function

“…In animal experimental epilepsy models, changes in cardiac rhythm have been elicited from both cortical and subcortical sites: the AMYG (in a kindling model) (248); in hemispherectomized rats (with penicillin-G induced thalamic and hypothalamic foci) (201); and with direct cortical stimulation of the marginal gyrus in cats (81). Regarding the insula, kainic acid injection into the rat right insula (197) increased blood pressure and heart rate and elevated norepinephrine levels in tandem with insular localized seizures.…”

Sudden unexpected death in epilepsy: From animals to humans

“…Changes in baseline heart rate and heart rate responses were evaluated during stage 5 of kindling, which corresponds to generalized seizures [26,27]. No significant differences in basal heart rate were found before and after electrode implantation, but the basal heart rate was higher during stage 5 of kindling, possibly resulting from sympathetic activation caused by the epileptic condition [26,27]. As found in previous studies [29], an intense bradycardia occurred at the beginning of the seizures, followed by a rebound tachycardia [26,27].…”

“…No significant differences in basal heart rate were found before and after electrode implantation, but the basal heart rate was higher during stage 5 of kindling, possibly resulting from sympathetic activation caused by the epileptic condition [26,27]. As found in previous studies [29], an intense bradycardia occurred at the beginning of the seizures, followed by a rebound tachycardia [26,27]. The intensity of the tachycardia was correlated with the number of generalized seizures, suggesting that these seizures have an effect on the autonomic nervous system [26,27].…”

“…A rat model of epilepsy is produced by repeated administration of an initially subconvulsive electrical stimulus to induce seizures that progressively become more intense [26,27]. The complete process involves five stages of increasingly intense seizures [28].…”

“…The complete process involves five stages of increasingly intense seizures [28]. Changes in baseline heart rate and heart rate responses were evaluated during stage 5 of kindling, which corresponds to generalized seizures [26,27]. No significant differences in basal heart rate were found before and after electrode implantation, but the basal heart rate was higher during stage 5 of kindling, possibly resulting from sympathetic activation caused by the epileptic condition [26,27].…”