Abstracts

Rationale: Vagus nerve stimulation (VNS) has proven to be an effective treatment for epilepsy and possibly depression. In addition to an acute abortive effect, VNS has subacute and chronic anti-convulsant effects. Such a time course is consistent with CNS biochemical changes. VNS in rats causes up-regulation of fos gene product expression in the brain and following cessation of a VNS train there is a gradual decline in anticonvulsant effect. Human CSF has been shown to be altered by VNS. The goal of the present study is to determine whether or not an anticonvulsive and/or antikindling property might be present in the CSF of animals that have been exposed to sub-acute/chronic (2 week) VNS.Methods: Twenty-three male Sprague-Dawley rats were randomly divided into two groups and given an intraventricular injection of cerebrospinal fluid obtained from donor rats treated with either VNS for 2 weeks or sham procedure. Following the injection, flurothyl myoclonic and tonic seizure threshold was measured. Seizure threshold was again measured daily for the following 3 consecutive days (4 days total). Results were analyzed using repeated measures mixed-model statistics.Results: The mean latency to myoclonic (VNS:104.32 ± 3.3s; Sham: 111.98 ± 3.2s ) and tonic (VNS:202.69 ± 8.4s; Sham: 207.45 ± 8.4s) seizure onset decreased significantly over the four days for each group (p<0.0001). There was no statisitical difference between the two groups for myoclonic or tonic seizure threshold. Plots of least square means for each of the end points are shown in figure 1.Conclusions: These preliminary results do not support the hypothesis that there is an anti-epileptic substance present in the CSF following subacute/chronic VNS. Further experiments are planned which will confirm or refute this finding and expand our understand of VNS and epilepsy.