Evidence for augmented brainstem activated forebrain seizures in Wistar Audiogenic Rats subjected to transauricular electroshock

Abstract

Previous work from our laboratory has shown that naïve Wistar Audiogenic Rats (WARs), a genetic model of reflex epilepsy in which seizures are induced by high-intensity sound stimulation (120 dB SPL), are seizure-prone to a variety of pro-convulsive stimuli (e.g., transauricular electroshock, pentylenetetrazole and pilocarpine). On the other hand, repetitive acoustic stimulation of WARs causes a slow recruitment of limbic structures, known as audiogenic kindling, changing seizure expression to include behavior characteristic of temporal-lobe epilepsy. Thus, our hypothesis is that WARs have facilitated acoustic-limbic projections when compared to Wistar controls. Wistar controls ( n = 9) and WARs ( n = 9) underwent EEG electrode implants in the cortex-Cx, amygdaloid complex-AMY and inferior colliculus-IC and received one low current transauricular electrical stimulus (ES) daily, for three consecutive days, with intensities of 10, 20 and 30 mA, respectively. The video-electroencephalographic activity was recorded 1 min before and 4 min after ES. Our results confirm previously described data indicating a greater susceptibility of WARs to seizure. However, low current ES (e.g., 20 mA) triggered epileptiform activity in the AMY only after epileptiform EEG was visible in the Cx and IC electrode leads. The AMY after-discharge continued even though no evident epileptiform activity was present in the Cx. In conclusion, our results add electrophysiological data to previously published behavioral evidence of WAR enhanced susceptibility to ES seizures and, also, support the hypothesis that the acoustic-limbic circuitry is facilitated even in unkindled WARs.