Stimulus and potassium-induced epileptiform activity in the human dentate gyrus from patients with and without hippocampal sclerosis

Stimulus and potassium-induced epileptiform activity in the human dentate gyrus from patients with and without hippocampal sclerosis

Author Gabriel, Siegrun Google Scholar
Njunting, Marleisje Google Scholar
Pomper, Joem K. Google Scholar
Merschhemke, Martin Google Scholar
Sanabria, Emidio RG Google Scholar
Eilers, Alexander. Google Scholar
Kivi, Anatol Google Scholar
Zeller, Melanie Google Scholar
Meencke, Heinz-Joachim Google Scholar
Cavalheiro, Esper Abrão Autor UNIFESP Google Scholar
Heinemann, Uwe Google Scholar
Lehmann, Thomas-Nicolas Google Scholar
Institution Johannes Mueller Inst Physiol
Charite Univ Med Berlin
Evangel Krankenhaus Konigin Elisabeth Herzberge
Universidade Federal de São Paulo (UNIFESP)
Abstract Hippocampal specimens resected to cure medically intractable temporal lobe epilepsy (TLE) provide a unique possibility to study functional consequences of morphological alterations. One intriguing alteration predominantly observed in cases of hippocampal sclerosis is an uncommon network of granule cells monosynaptically interconnected via aberrant supragranular mossy fibers. We investigated whether granule cell populations in slices from sclerotic and nonsclerotic hippocampi would develop ictaform activity when challenged by low-frequency hilar stimulation in the presence of elevated extracellular potassium concentration (10 and 12 mM) and whether the experimental activity differs according to the presence of aberrant mossy fibers.We found that ictaform activity could be evoked in slices from sclerotic and nonsclerotic hippocampi (27 of 40 slices, 14 of 20 patients; and 11 of 22 slices, 6 of 12 patients, respectively). However, the two patient groups differed with respect to the pattern of ictaform discharges and the potassium concentration mandatory for its induction. Seizure-like events were already induced with 10 mM K+. They exclusively occurred in slices from sclerotic hippocampi, of which 80% displayed stimulus-induced oscillatory population responses (250-300 Hz). in slices from nonsclerotic hippocampi, atypical negative field potential shifts were predominantly evoked with 12 mM K+. in both groups, the ictaform activity was sensitive to ionotropic glutamate receptor antagonists and lowering of [Ca2+](o).Our results show that, in granule cell populations of hippocampal slices from TLE patients, high K+-induced seizure-like activity and ictal spiking coincide with basic electrophysiological abnormalities, hippocampal sclerosis, and mossy fiber sprouting, suggesting that network reorganization could play a crucial role in determining type and threshold of such activity.
Keywords hippocampus
Ammon's horn sclerosis
mesial temporal lobe epilepsy
mossy fiber sprouting
high potassium
bicuculline
ictaform events
Language English
Date 2004-11-17
Published in Journal of Neuroscience. Washington: Soc Neuroscience, v. 24, n. 46, p. 10416-10430, 2004.
ISSN 0270-6474 (Sherpa/Romeo, impact factor)
Publisher Soc Neuroscience
Extent 10416-10430
Origin http://dx.doi.org/10.1523/JNEUROSCI.2074-04.2004
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000225165500016
URI http://repositorio.unifesp.br/handle/11600/28020

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