Intra-Amygdaloid Injection of Kainic Acid in Rats with Genetic Absence Epilepsy: The Relationship of Typical Absence Epilepsy and Temporal Lobe Epilepsy

Abstract

We showed previously that genetic absence epilepsy rats from Strasbourg (GAERS) resist secondary generalization of focal limbic seizures after electrical kindling. We now investigate the effect of intra-amygdaloid injection of kainic acid, as another model of temporal lobe epilepsy, focusing on epileptogenesis, spike-and-wave discharges (SWDs), and the transition from basal to SWD states in GAERS. The EEG was recorded from the hippocampus and cortex of adult GAERS and Wistar rats before kainic acid injections into the basolateral amygdala and for 3 months thereafter. EEG and video recordings monitored SWDs and convulsive seizures. We analyzed spectral changes of the EEG during kainic acid-induced status epilepticus, SWDs, for 10 s before (silent period) and for 2 s before (transition period) SWDs. After the injection of kainic acid, all animals experienced convulsive seizures for at least 3 h. The first convulsive seizure was significantly delayed in GAERS compared with Wistar rats. SWDs and increases in power of the delta, alpha, and beta frequency ranges during the transition period disappeared after the kainic acid injection for 1-3 d and gradually reappeared. Power increases in the delta and alpha ranges were significantly correlated with the number of SWDs, in the beta and alpha ranges with their mean duration. Neo-Timm's staining at the end of experiments demonstrated that mossy fiber sprouting in GAERS is less pronounced than in Wistar rats. Our findings show that mechanisms underlying absence epilepsy and temporal lobe epilepsy interact with each other, although a site of this interaction remains to be defined.

Antiepileptic action of N-palmitoylethanolamine through CB1 and PPAR-α receptor activation in a genetic model of absence epilepsy

“…On the other side, absence animal models of epilepsy, such as WAG/Rij and GAERS rats, are resistant to amygdaloid kindling (Onat et al, 2007) and the demonstration that suppression of absence seizures by intracortical injection of ethosuximide reduces the resistance to kindling also supports a correlation between thalamo-cortical alterations and amygdala (Gülhan Aker et al, 2010). Furthermore, a not defined correlation between absence seizures and temporal lobe epilepsy has been previously demonstrated by injecting kainic acid into the amygdala of GAERS (Gurbanova et al, 2008).…”

Long-term outcomes in patients with West syndrome: An outpatient clinical study

“…However, the EEG correlates of these spasms, despite variable morphological characteristics, are almost always a generalized paroxysmal discharge, even in patients with hemihypsarrhythmia [17]. A delayed effect of generalized epilepsy on the onset of experimental focal seizures in some studies on adult rats with genetically determined deficiencies was reported previously [18,19]. Here, the situation was the opposite, suggesting that the focal firing can produce a delayed effect on the maturational processes including myelination, which are necessary for generalization of epileptic discharges.…”

Space–time network connectivity and cortical activations preceding spike wave discharges in human absence epilepsy: a MEG study

“…Interestingly, genetic epileptic WAG/Rij rats have also clear low frequency delta activity prior to the onset of SWDs in cortex and thalamus [50]; it is also likely that synchronized activity in cortex and thalamus builds up or reduces before SWD onset, rather than being a sudden generalized synchronous event. The latter has also been proposed in WAG/ Rij rats based on outcomes of classical FFTs, NA analyses, and wavelet analyses [14,28,43]. However, the current study is a preliminary study and it needs to be assessed with a larger data set.…”