Fig. 3

Simulation of seizure-induced asystole and demonstration of impact on seizure activity. a–e Taken from [60] with permission. After complete vagal transection, vagal afferent (stimulation of the central segment of the vagus) or vagal efferent (stimulation of the peripheral segment of the vagus) stimulation was tested at 10 or 50 Hz. Neither 10-Hz (a) nor 50-Hz (b) afferent vagal stimulation had an impact on heart rate (red sweep in each panel) or kainic acid-induced seizure activity (top green sweep in each panel). Efferent vagal stimulation at 10 Hz (c) slowed the heart, but did not significantly alter brain blood flow (blue and middle green sweeps). Efferent vagal stimulation at 50 Hz (d) produced asystole, a significant drop in systemic blood pressure and significant decreases in brain blood flow, stopping the seizure. Seizure activity resumed after the stimulation because the chemical convulsant is still present. Phentolamine infusion (e) for peripheral vasodilation to decrease systemic blood pressure had similar effects to the vagus nerve stimulation-induced asystole. To the right is another segment of the full schematic shown in Fig. 9. This segment emphasizes a different sequence of events: seizure activity changes autonomic activity; asystole occurs; asystole causes the seizure activity to end; autonomic activity returns to pre-seizure levels. The main point to emphasize is that the evidence indicates that seizure-induced asystole will be self-terminating because these episodes terminate the seizures that underlie the autonomic derangement