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Updated: Sep 22, 2025
Electroconvulsive Seizures in Rats and Fractionation of Their Hippocampi to Examine Seizure-induced Changes in Postsynaptic Density Proteins
Published on: August 15, 2017
Impact of Raptor and Rictor Deletion on Hippocampal Pathology Following Status Epilepticus
Christin M Godale1,2, Emma V Parkins3,2, Christina Gross3,2,4
1Department of Anesthesia, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, CincinnatiCincinnati, OH, ML200145229, USA.
Abstract:
Neuronal hyperactivation of the mTOR signaling pathway may play a role in driving the pathological sequelae that follow status epilepticus. Animal studies using pharmacological tools provide support for this hypothesis, however, systemic inhibition of mTOR-a growth pathway active in every mammalian cell-limits conclusions on cell type specificity. To circumvent the limitations of pharmacological approaches, we developed a viral/genetic strategy to delete Raptor or Rictor, inhibiting mTORC1 or mTORC2, respectively, from excitatory hippocampal neurons after status epilepticus in mice. Raptor or Rictor was deleted from roughly 25% of hippocampal granule cells, with variable involvement of other hippocampal neurons, after pilocarpine status epilepticus. Status epilepticus induced the expected loss of hilar neurons, sprouting of granule cell mossy fiber axons and reduced c-Fos activation. Gene deletion did not prevent these changes, although Raptor loss reduced the density of c-Fos-positive granule cells overall relative to Rictor groups. Findings demonstrate that mTOR signaling can be effectively modulated with this approach and further reveal that blocking mTOR signaling in a minority (25%) of granule cells is not sufficient to alter key measures of status epilepticus-induced pathology. The approach is suitable for producing higher deletion rates, and altering the timing of deletion, which may lead to different outcomes.
Insights
Targeting the mTOR pathway after seizures shows promise. Genetic deletion of mTORC1 or mTORC2 in a small percentage of neurons did not prevent status epilepticus pathology.
Area of Science:
- Neuroscience
- Cellular Biology
- Signaling Pathways
Background:
- Neuronal hyperactivation of the mechanistic target of rapamycin (mTOR) signaling pathway is implicated in the pathology following status epilepticus.
- Systemic mTOR inhibition offers limited insight into cell-type-specific roles due to mTOR's ubiquitous activity.
Purpose of the Study:
- To develop and utilize a viral/genetic strategy for cell-type-specific mTOR inhibition in excitatory hippocampal neurons post-status epilepticus.
- To investigate the impact of inhibiting mTORC1 (via Raptor deletion) or mTORC2 (via Rictor deletion) on neuronal pathology after induced seizures.
Main Methods:
- Developed a viral/genetic system to delete Raptor or Rictor in mouse hippocampal neurons after pilocarpine-induced status epilepticus.
- Achieved deletion in approximately 25% of hippocampal granule cells, with some impact on other neuron types.
- Assessed status epilepticus-induced changes including hilar neuron loss, mossy fiber sprouting, and c-Fos activation.
Main Results:
- Status epilepticus induced expected pathological changes, which were not prevented by gene deletion.
- Raptor deletion led to a relative decrease in c-Fos-positive granule cells compared to Rictor deletion groups.
- The genetic approach effectively modulated mTOR signaling, but deletion in a minority of cells did not alter key pathological measures.
Conclusions:
- The viral/genetic strategy is effective for modulating mTOR signaling in a cell-specific manner.
- Inhibiting mTORC1 or mTORC2 in a small fraction (25%) of excitatory hippocampal neurons is insufficient to mitigate major pathological outcomes of status epilepticus.
- Future studies could explore higher deletion rates or altered deletion timing for potentially different results.
