Synchronous inhibitory potentials precede seizure-like events in acute models of focal limbic seizures

Laura Uva, Gian Luca Breschi, Vadym Gnatkovsky, Stefano Taverna, Marco de Curtis

Research output: Contribution to journalArticle

Abstract

Interictal spikes in models of focal seizures and epilepsies are sustained by the synchronous activation of glutamatergic and GABAergic networks. The nature of population spikes associated with seizure initiation (pre-ictal spikes; PSs) is still undetermined.Weanalyzed the networks involved in the generation of both interictal and PSs in acute models of limbic cortex ictogenesis induced by pharmacological manipulations. Simultaneous extracellular and intracellular recordings from both principal cells and interneurons were performed in the medial entorhinal cortex of the in vitro isolated guinea pig brain during focal interictal and ictal discharges induced in the limbic network by intracortical and brief arterial infusions of either bicuculline methiodide (BMI) or 4-aminopyridine (4AP). Local application of BMI in the entorhinal cortex did not induce seizure-like events (SLEs), but did generate periodic interictal spikes sensitive to the glutamatergic non-NMDA receptor antagonist DNQX. Unlike local applications, arterial perfusion of either BMI or 4AP induced focal limbic SLEs. PSs just ahead of SLE were associated with hyperpolarizing potentials coupled with a complete blockade of firing in principal cells and burst discharges in putative interneurons. Interictal population spikes recorded from principal neurons between two SLEs correlated with a depolarizing potential. We demonstrate in two models of acute limbic SLE that PS events are different from interictal spikes and are sustained by synchronous activation of inhibitory networks. Our findings support a prominent role of synchronous network inhibition in the initiation of a focal seizure.

Original languageEnglish
Pages (from-to)3048-3055
Number of pages8
JournalJournal of Neuroscience
Volume35
Issue number7
DOIs
Publication statusPublished - Feb 18 2015

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Keywords

  • Acute seizure model
  • Entorhinal cortex
  • Focal seizures
  • In vitro guinea pig brain
  • Interictal spikes
  • Pre-ictal spikes

ASJC Scopus subject areas

  • Neuroscience(all)
  • Medicine(all)

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