Comprehensive evaluation of neurosteroid monotherapy and neurosteroid-midazolam combination therapy in mitigating the nerve agent soman-induced chronic neuropsychiatric dysfunction, epileptogenesis, neuroinflammation and neurodegeneration in pediatric models.

Children are especially vulnerable to the neurotoxic effects of nerve agents, which can cause lasting neuronal dysfunction, including cognitive impairments, epilepsy, and related comorbidities. Current benzodiazepine anticonvulsants often fail to prevent long-term neuropathology following neurotoxic chemical exposure, underscoring the urgent need for more effective treatments. This study investigated the therapeutic potential of the synthetic neurosteroid ganaxolone (GX) in a pediatric rat model of the nerve agent soman exposure. Pediatric (postnatal day 21) rats were acutely exposed to soman and received GX alone or in combination with midazolam treatment 40 min later. Continuous video-EEG monitoring, behavioral assessments and MRI imaging were conducted over a 3-month period after the acute challenge. Soman exposure led to persistent epileptic seizures, electrographic ictal biomarkers, cognitive dysfunction, behavioral impairments, hippocampal atrophy, neuroinflammation and neurodegeneration. Midazolam alone had minimal neuroprotective effects. In both monotherapy and combination regimen, GX significantly reduced memory deficits, anxiety, and depressive-like behaviors. GX attenuated spontaneous seizures and suppressed non-convulsive epileptiform discharges, interictal spikes, and high-frequency oscillations, suggesting disease-modifying effects. Mechanistic immunohistology analyses showed that GX preserved parvalbumin-positive inhibitory interneurons and NeuN-positive principal neurons, enhanced doublecortin-positive neurogenesis in the hippocampus, and reduced inflammatory microgliosis as indicated by IBA1 expression. MRI scans confirmed reduced neuropathological changes in GX-treated animals. Collectively, these findings demonstrate that GX alone or in combination with midazolam offers strong neuroprotective, antiepileptogenic, and anti-inflammatory benefits, highlighting its promise as a robust pediatric anticonvulsant for nerve agent-induced seizures and long-term neurologic dysfunction.