Acute hyperexcitability differentially affects hippocampal neurogenesis features and spatial memory.

Area of Science:

• Neuroscience
• Epilepsy Research
• Cell Biology

Background:

• Epileptic seizures are known to disrupt adult hippocampal neurogenesis (AHN).
• The precise impact of varying seizure intensities on AHN and cognitive functions remains incompletely understood.

Purpose of the Study:

• To investigate how different seizure severities affect adult hippocampal neurogenesis and associated memory functions.
• To examine the morphological and synaptic changes in adult-born granule cells (abGCs) following acute hyperexcitability.

Main Methods:

• Administered low (5 mg/kg) or high (25 mg/kg) dose kainic acid (KA) to induce varying seizure severity in mice.
• Utilized genetic labeling to track progenitor cells and their progeny in the dentate gyrus.
• Recorded EEG, assessed spatial and contextual fear memory, and analyzed abGCs 32 days post-treatment.

Main Results:

• High-dose KA induced more severe seizures, increased mature abGCs with altered positioning, and elevated dendritic spine density.
• Low-dose KA resulted in presynaptic bouton enlargement in abGCs.
• Both doses impaired spatial recognition memory but preserved contextual fear memory.

Conclusions:

• Acute seizure severity differentially modulates the morphological and synaptic characteristics of adult-born granule cells.
• Hyperexcitability selectively disrupts hippocampal-dependent spatial memory.
• Seizure severity exerts qualitative effects on both neurogenesis and cognitive function.