Progressive brain damage, synaptic reorganization and NMDA activation in a model of epileptogenic cortical dysplasia

PLoS One. 2014 Feb 27;9(2):e89898. doi: 10.1371/journal.pone.0089898. eCollection 2014.

Abstract

Whether severe epilepsy could be a progressive disorder remains as yet unresolved. We previously demonstrated in a rat model of acquired focal cortical dysplasia, the methylazoxymethanol/pilocarpine - MAM/pilocarpine - rats, that the occurrence of status epilepticus (SE) and subsequent seizures fostered a pathologic process capable of modifying the morphology of cortical pyramidal neurons and NMDA receptor expression/localization. We have here extended our analysis by evaluating neocortical and hippocampal changes in MAM/pilocarpine rats at different epilepsy stages, from few days after onset up to six months of chronic epilepsy. Our findings indicate that the process triggered by SE and subsequent seizures in the malformed brain i) is steadily progressive, deeply altering neocortical and hippocampal morphology, with atrophy of neocortex and CA regions and progressive increase of granule cell layer dispersion; ii) changes dramatically the fine morphology of neurons in neocortex and hippocampus, by increasing cell size and decreasing both dendrite arborization and spine density; iii) induces reorganization of glutamatergic and GABAergic networks in both neocortex and hippocampus, favoring excitatory vs inhibitory input; iv) activates NMDA regulatory subunits. Taken together, our data indicate that, at least in experimental models of brain malformations, severe seizure activity, i.e., SE plus recurrent seizures, may lead to a widespread, steadily progressive architectural, neuronal and synaptic reorganization in the brain. They also suggest the mechanistic relevance of glutamate/NMDA hyper-activation in the seizure-related brain pathologic plasticity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Atrophy
  • Cerebral Cortex / pathology
  • Disease Models, Animal
  • Epilepsies, Partial / etiology*
  • Epilepsies, Partial / pathology*
  • Female
  • Hippocampus / pathology
  • Malformations of Cortical Development / chemically induced
  • Malformations of Cortical Development / complications*
  • N-Methylaspartate / metabolism*
  • Neocortex / pathology
  • Pregnancy
  • Pyramidal Cells / pathology
  • Rats
  • Receptors, N-Methyl-D-Aspartate / metabolism
  • Synapses / pathology*

Substances

  • Receptors, N-Methyl-D-Aspartate
  • N-Methylaspartate

Grants and funding

This work was supported by the Italian Ministry of Health, and by the “Sovvenzione Globale Ingenio – Regione Lombardia” from the Social European Fund (Grant n. A0000844). No additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.