Vagus nerve stimulation suppresses generalized seizure activity and seizure-triggered postictal cardiac rhythm changes in rats

In the present study, we investigated the effects of vagus nervestimulation (VNS), a proposed treatment for patients withintractable epilepsy, on cardiac rhythm following seizures inducedby pentylenetetrazole (PTZ) in Wistar rats. After a baselinerecording of electroencephalogram (EEG), electrocardiogram(ECG) and blood pressure (BP), rats in the first group received asingle convulsive dose of PTZ (70 mg/kg) (Group 1). In the othertwo groups, the Wistar rats were implanted with a cuff electrodeon the left cervical vagus nerve. One day after surgery, rats inthe second group were treated with VNS (Group 2), whereas ratsin the third group were connected to the stimulator but did notreceive VNS (Group 3). Ten minutes after VNS onset, 70 mg/kgdose of PTZ was injected. EEG, ECG and BP were continuouslyrecorded during post-injection period. Seizure severity wasscored behaviorally. Then, baseline, ictal and postictal periodswere analyzed for cardiac rhythms, seizure severity and bloodpressure variability. PTZ treatment induced tonic-clonic seizureactivity in all animals of Group 1 and Group 3. In these groups amarked increase of mean arterial blood pressure (MABP) but asignificant decrease in heart rate and PP interval fluctuations wasobserved at postictal period. However, in the VNS-treated groupthe seizure scores and cardiac parameter returned to thebaseline level. Present results emphasize that VNS effectivelyreduces seizure severity and suppress the seizure-inducedcardiac rhythm changes.