Evaluation of behavioral parameters and mortality in a model of temporal lobe epilepsy induced by intracerebroventricular pilocarpine administration

Abstract

The pilocarpine model of temporal lobe epilepsy (TLE) is a useful tool that is used to investigate the mechanisms underlying the generation and maintenance of seizures. Although this model has been modified significantly to reduce mortality and to promote the appearance of spontaneous recurrent seizures, to date, no detailed evaluation has been performed of the behavioral parameters and mortality in TLE induced by intracerebroventricular pilocarpine administration; therefore, this was the goal of the present study. A single dose of pilocarpine hydrochloride (2.4 mg in a total volume of 2 µl) was injected into the right lateral brain ventricle of rats; the convulsive behavior was rated using the Racine scale and the mortality was analyzed in these animals. We found that 30-90 min after animals received intracerebroventricular pilocarpine injections, 73% developed status epilepticus (SE) with an activity score of 4/5 on the Racine scale. Moreover, these seizures were associated with the propagation of epileptiform activity to different hippocampal regions. Of the animals that developed SE, spontaneous recurrent seizures were observed in 32.5% at different times after SE induction. A 35% mortality rate was observed, which included animals that died during pilocarpine injection and after SE induction. On the basis of these findings, and given the observed latency between the insult (SE induction by pilocarpine injection) and the manifestation of spontaneous recurrent seizures, we propose that this model is a useful tool for basic biomedical research of SE and TLE.