Neurodevelopmental Alterations in Inhibitory Interneurons of Cortex, Hippocampus, and Striatum of Genetic Absence Epilepsy Rats.

AIMS: Absence seizures, characterized by spike-and-wave discharges (SWDs), are mediated by reciprocal thalamocortical interactions; however, the contribution of developing inhibitory networks to SWDs remains unclear. We investigated the developmental trajectory of inhibitory interneurons in Genetic Absence Epilepsy Rats from Strasbourg (GAERS) by analyzing their distribution across postnatal development in the somatosensory (S1) and motor (M1) cortices, the hippocampus, and striatum. METHODS: The neurodevelopmental trajectory of parvalbumin-positive (PV+) and somatostatin-positive (SST+) interneurons was quantified at three critical stages: postnatal day 14 (P14), when SWDs were not yet observed, P21 when immature SWDs appear, and adulthood (P90), when mature SWDs are established. Wistar rats served as controls. Brain sections were processed immunohistochemically to quantify interneuron density. RESULTS: PV+ interneuron density across S1 and M1 was significantly higher in GAERS at P14 than control. However, this difference was not maintained at P21 and adults. Conversely, SST+ interneurons exhibited a delayed increase in M1. GAERS displayed higher PV+ interneuron density in the dentate gyrus and CA1 at P14, whereas SST+ interneuron density remained unchanged across hippocampal subfields. Striatal PV+ and SST+ interneurons increased at later developmental stages, suggesting altered inhibition in basal ganglia. CONCLUSION: These findings demonstrate a temporally dynamic and region-specific reorganization of interneurons in GAERS that may underlie absence epileptogenesis.