Tag Archives: temporal lobe epilepsy

The effect of amygdala low-frequency stimulation on inter-hippocampal connectivity in the pilocarpine model of epilepsy

DOI: 10.2478/amma-2021-0004

Objective: The aim of our study was to investigate the effect of amygdala low-frequency stimulation on inter-hippocampal network synchronization by using the phase locking value (PLV) in order to establish new biomarkers of treatment efficacy in a temporal lobe epilepsy model.
Materials and Methods: The lithium-pilocarpine model of epilepsy was used to induce status epilepticus in male Wistar rats. Afterward, seizures were scored based on continuous video recordings. 8 weeks after status epilepticus electrodes were implanted: a stimulating electrode in the left basolateral amygdala and bilaterally two hippocampal recording electrodes in both pilocarpine-treated and age-matched control rats (N=7). 10 Pilo and 4 control animals were stimulated daily for 10 days with 4 packages of 50 seconds 4Hz trains. Inter-hippocampal PLVs were measured offline before and after stimulation trains in delta (1-4Hz), theta (4-12Hz), gamma (30-100Hz), HFO (100-150Hz), ripple (150-250Hz), and fast ripple (250-600Hz) bands using Brainstorm software.
Results: The PLV before the stimulation was significantly lower in epileptic animals compared to controls in the delta, theta, and gamma bands. The PVLs of epileptic animals were increased by low-frequency stimulation in delta and theta bands. The PLVs in HFO and ripple band correlated positively with the changes in seizure rate, while the PLVs in the delta, theta, and gamma correlated positively with the changes in seizure duration.
Conclusion: Amygdala low-frequency stimulation improved the impaired synchrony between the two hippocampi in low-frequency bands. The phase locking value could be useful to evaluate the efficiency of therapeutic interventions in temporal lobe epilepsy.

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Cortical Epileptogenesis of Slowly Kindled Freely Moving Rats

DOI: 10.1515/amma-2015-0003

Objective. Epilepsy is a neurological disorder that can be caused by many underlying pathologies. The epileptic and interictal manifestations that appear during the progression of chronic epilepsy are still not understood completely. One of the most frequent forms of this disease is temporal lobe epilepsy in which is clear involvement of the hippocampal formation. In order to study the electrografic progression of untreated seizures we used amygdala kindling in freely moving rats.
Methods. Seven animals were implanted with bilateral hippocampal and prefrontal electrodes. A bipolar electrode, implanted in the lateral nuclei of the left amygdala was used for stimulation. The kindled group of animals was stimulated daily with the minimum current intensity needed to reach the afterdischarge threshold. Behavioral changes during kindling were scored according to the Racine scale.
Results. The average seizure severity on the Racine scale was 2.6±0.4 by day 6 and 4.4±0.6 by day 20. The first spontaneous seizures appeared after 31 days of stimulation. During spontaneous seizures the preictal spike full width at half maximum increased gradually from 51±4msec to 110±5msec (p < 0.05) whereas the amplitude of the negative field potential deflection increased by 62% (p < 0.05).
|Conclusions. Our study showed that the progression of temporal lobe epilepsy, as seen in humans, can be reproduced in the kindling model with high fidelity. This study confirms in vivo the increase in preictal spike duration as well as the increase of the amplitude of negative field potential deflection during the preictal period.

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