Absence-like seizures in adult rats following pilocarpine-induced status epilepticus early in life

Abstract

Administration of pilocarpine causes epilepsy in rats if status epilepticus (SE) is induced at an early age. To determine in detail the electrophysiological patterns of the epileptogenic activity in these animals, 46 Wistar rats, 7-17 days old, were subjected to SE induced by pilocarpine and electro-oscillograms from the cortex, hippocampus, amygdala, thalamus and hypothalamus, as well as head, rostrum and vibrissa, eye, ear and forelimb movements, were recorded 120 days later. Six control animals of the same age range did not show any signs of epilepsy. In all the rats subjected to SE, iterative spike-wave complexes (8.1 ± 0.5 Hz in frequency, 18.9 ± 9.1 s in duration) were recorded from the frontal cortex during absence fits. However, similar spike-wave discharges were always found also in the hippocampus and, less frequently, in the amygdala and in thalamic nuclei. Repetitive or single spikes were also detected in these same central structures. Clonic movements and single jerks were recorded from all the rats, either concomitantly with or independently of the spike-wave complexes and spikes. We conclude that rats made epileptic with pilocarpine develop absence seizures also occurring during paradoxical sleep, showing the characteristic spike-wave bursts in neocortical areas and also in the hippocampus. This is in contrast to the wellaccepted statement that one of the main characteristics of absence-like fits in the rat is that spike-wave discharges are never recorded from the hippocampal fields. Correspondence

Behavioral impairments in rats with chronic epilepsy suggest comorbidity between epilepsy and attention deficit/hyperactivity disorder

“…Neuroprotection in limbic areas afforded by acute treatment of pilocarpine SE by carisbamate resulted in the displacement of secondary generalized complex partial seizures by absence-like seizures [56]. SE induced by pilocarpine in neonatal rats (the latter developing significantly milder injury in limbic structures than adults [49, 57, 58]), resulted in absence-like seizures during the adulthood [59]. It is therefore possible that allowing SE to resolve without diazepam+phenytoin treatment would prevent the occurrence of ADHD-like abnormalities.…”

The pilocarpine model of temporal lobe epilepsy: Marked intrastrain differences in female Sprague–Dawley rats and the effect of estrous cycle

“…Most laboratories have used male rats to limit the influences of variations in the activity of sex hormone-related axes and also because of the different modulatory effects of testosterone and estradiol on seizures [3]. Studies aimed at comparing the different responses in Wistar males and females [10][11][12] have failed to find evidence for any differences in behavior, EEG, or occurrence of SRS.…”

An Acquired Channelopathy Involving Thalamic T-Type Ca2+Channels after Status Epilepticus

“…A RE-TRN-CA1 loop may amplify ictal activity in the hippocampus, leading to seizure generalization by recruiting additional thalamocortical circuits into synchronized activity. Interestingly, Ferreira et al (2003) recorded synchronized absence-like spike-wave discharges (SWD) from the thalamus, hippocampus and cortex of adult rats that had experienced pilocarpine-induced SE. These SWD were abolished with ethosuximide, a broad-spectrum T-type channel blocker.…”