Seizure-induced strengthening of a recurrent excitatory circuit in the dentate gyrus is proconvulsant

Kaoutsar Nasrallah, M. Agustina Frechou, Young J. Yoon, Subrina Persaud, J. Tiago Goncalves, Pablo E. Castillo

Research output: Contribution to journalArticlepeer-review

Abstract

Epilepsy is a devastating brain disorder for which effective treatments are very limited. There is growing interest in early intervention, which requires a better mechanistic understanding of the early stages of this disorder. While diverse brain insults can lead to epileptic activity, a common cellular mechanism relies on uncontrolled recurrent excitatory activity. In the dentate gyrus, excitatory mossy cells (MCs) project extensively onto granule cells (GCs) throughout the hippocampus, thus establishing a recurrent MC-GC-MC excitatory loop. MCs are implicated in temporal lobe epilepsy, a common form of epilepsy, but their role during initial seizures (i.e., before the characteristic MC loss that occurs in late stages) is unclear. Here, we show that initial seizures acutely induced with an intraperitoneal kainic acid (KA) injection in adult mice, a wellestablished model that leads to experimental epilepsy, not only increased MC and GC activity in vivo but also triggered a brain-derived neurotrophic factor (BDNF)-dependent long-term potentiation (LTP) at MC-GC excitatory synapses. Moreover, in vivo induction of MC-GC LTP using MC-selective optogenetic stimulation worsened KA-induced seizures. Conversely, Bdnf genetic removal from GCs, which abolishes LTP, and selective MC silencing were both anticonvulsant. Thus, initial seizures are associated with MC-GC synaptic strengthening, which may promote later epileptic activity. Our findings reveal a potential mechanism of epileptogenesis that may help in developing therapeutic strategies for early intervention.

Original languageEnglish (US)
Article numbere2201151119
JournalProceedings of the National Academy of Sciences of the United States of America
Volume119
Issue number32
DOIs
StatePublished - Aug 9 2022

Keywords

  • BDNF
  • epilepsy
  • granule cell
  • hippocampus
  • mossy cell

ASJC Scopus subject areas

  • General

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