Authors :
Presenting Author: Marin Furukuwa, Undergraduate – University of California, Riverside
F.J. Guevara-Pantoja, PhD – University of California, Riverside
Viji Santhakumar, PhD – University of California, Riverside
Rationale:
Temporal lobe epilepsy is a disorder defined by recurrent spontaneous seizures that affects the dentate gyrus (DG), a circuit within the hippocampus. DG activity is heavily regulated by diverse inhibitory neurons that use GABA as their primary neurotransmitter. Specifically, parvalbumin (PV) and somatostatin (SST) expressing interneurons (INs) provide inhibition to distinct zones of granule cell dendrites. Seizures lead to loss and reorganization of IN subtypes, which could impact DG excitability and the onset and termination of seizures. However, how PV and SST INs shape the activity patterns within seizures is unknown.Methods:
A cohort of epileptic mice, previously subjected to acute kainic acid (KA) induced seizures, and saline injected controls were examined 4 weeks after seizure induction for chemically evoked electrographic seizures. Mice, with virally-driven GCaMP expression in specific interneuron subtypes, underwent EEG and calcium fiberphotometry. One day after recordings, mice were fixed under anesthesia and brains were recovered for histology. Brain slices were immunostained to quantify interneuron subtypes and neurochemical markers of activity (cFOS and deltaFosB).
Results:
Following acute KA-induced seizures, there was a decrease in the number of PV+ INs in epileptic mice compared to controls (average count per slice, control: 11.8±1.77, epileptic: 3.71±1.32, n=3 mice each, p< 0.05, unpaired t-test). While there was no increase in cFOS+ cells in epileptic mice (average count per slice, control: 8.48±2.09, epileptic: 6.53±2.83, n=3 mice each, p > 0.05, unpaired t-test). DeltaFosB expression was increased (average count per slice, control: 102.02±14.84, epileptic: 260.26±86.17, n=3 mice each, p< 0.05, unpaired T-test) in epileptic mice.