Effects of vagus nerve stimulation on seizure in animals with epilepsy

Lanfeng ZHAO; Jingjin LI; Yangyuan AN; Yizhen WANG

ABSTRACT

BACKGROUND:

Vagus nerve stimulation (VNS) is a neurophysiological therapy (NPT) of refractory epilepsy, which can control the seizure by stimulating the vagus nerve stem in cervical part.

OBJECTIVE:

To study the effect of intermittent left-side VNS on seizure of epileptic animals, and provide theoretic basis for the interaction of somatic information and that of internal organs.

DESIGN:

Observation study.

SETTING:

Department of Neurobiology, Capital University of Medical Science.MATERIALS The experiment was performed in the Laboratory of Electrophysiology in Department of Neurobiology, Capital University of Medical Science from March 2000 to September 2002. Thirty-four healthy adult SD rats and 8 rabbits, weighting (220-250) g and (2.2-2.5) kg respectively were selected.

METHODS:

①Ten rats were intramuscularly injected with (150 000-160 000) U of penicillin (PCN). VNS effects on epileptiform activities of rats were studied by observing the changes in electrocorticogram (ECoG)and behavior of rats before and after VNS.②(0.24-0.48) mg of PCN was injected into the hippocampus of another 8 rabbits to induce epilepsy, and VNS effects on ECoG of epileptic rats were observed. ③Seizures of 16 rats were induced by Kainic acid, and changes in discharge activity of hippocampal neuron, ECoG and behavior of epileptic rats were observed after VNS. ④Seizures of 8 rabbits were induced by cortical injection of strychnine with microinjector, and VNS effects on ECoG of rabbits with epilepsy induced by acute cortical injury were observed.MAIN OUTCOME

MEASURES:

①VNS effects on seizure of rats with epilepsy induced by PCN. ②VNS effects on seizure of rats with epilepsy induced by Kainic acid. ③VNS effects on epileptiform ECoG of rabbits with epilepsy induced by strychnine.

RESULTS:

A total of 34 rats and 8 rabbits were involved in the analysis of results. VNS could remarkably suppress the seizure of epileptic animals,and epileptiform ECoG, epileptiform discharges of hippocampal neuron and behavior significantly changed with the total effective rate greater than 50%. The total effective rate of VNS before seizure was greater than 80%.In epilepsy group indoeed by intramuscular injection of PCN, ECoG and behavior were markedlly aneliorated respectively for 40% and 50% of rats.In epilepsy group induced by injection of PCN in hippocampus, the ECoG was siguificantly ameliorated in 50% rats. In epileptic rabbit group induced by partial injection of strychnine via cerebral cortex, the epilepti form wave iu ECoG was controlled by VNS in 50 % of animals.

CONCLUSION:

VNS can effectively suppress seizure of epileptic animals. The antiepileptic effect of VNS is associated with cerebral cortical aud hippcampal neurons. Somatic epileptiform activity could be effectively inhibited by the integration of visceral afferent information in cortical and hippocampal parts.