Ictogenesis and epileptogenesis in EL mice

Area of Science:

• Neuroscience
• Epilepsy Research
• Molecular Biology

Background:

• Epilepsy involves abnormal neural plasticity, potentially linked to nitric oxide (NO) synthetases (nNOS, eNOS) crucial for neuronal plasticity.
• Understanding the roles of NO synthetases and immediate early genes (IEGs) in ictogenesis and epileptogenesis is vital for epilepsy research.

Purpose of the Study:

• To investigate ictogenesis and epileptogenesis in EL mice by examining alterations in NO synthetases, IEG expression, and GABA distribution.
• To explore the developmental and seizure-history-dependent changes in these molecular markers.

Main Methods:

• In situ hybridization for IEG (c-fos, zif) expression.
• Ultramicroenzymatic chemistry for GABA concentrations and GAD activities.
• Immunoblotting for NOS isoforms and TUNEL assay for DNA fragmentation.

Main Results:

• IEG expression in EL mice correlated with seizure history, threshold, and age, notably in the hippocampal CA1 region.
• Altered GABA concentrations and GAD activities were observed in brain regions with altered IEG expression.
• nNOS and iNOS, and to a lesser extent eNOS, were essential for ictogenicity and epileptogenicity, with DNA fragmentation in the hippocampus during interictal periods.

Conclusions:

• Continuous IEG expression and abnormal GABAergic function are implicated in epileptogenesis, while transient IEG expression is linked to ictogenesis.
• An imbalance of iNOS (excess) and eNOS (deficit) may contribute to seizure focus and ictogenesis.
• Modulating iNOS and eNOS activity presents a potential therapeutic strategy for novel antiepileptic drugs.