164 Astrocytes With Prior Exposure to Serum Predispose Cortical Networks to Develop Hypersynchrony and Bursting Activity in Response to Cytokines

INTRODUCTION: Intracranial hemorrhage and infection during the perinatal period are known risk factors for neonatal seizures, with up to 25% of patients with neonatal seizures developing epilepsy later in life. However, the underlying mechanisms that facilitate the development of epilepsy following provoked neonatal seizures remain unclear. METHODS: A neuron-astrocyte coculture system was employed to model perinatal cortical development and characterize the combinatorial effects of serum and cytokine exposures on cortical network activity and synchrony. Cortical neurons isolated from embryonic day 15.5 (E15.5) C57BL/6J mice were cocultured with primary cortical astrocytes that were either exposed to serum or vehicle prior to a washout period and allowed to develop into functional cortical networks. Calcium imaging of individual neuron and ensemble activity was achieved using a synapsin-driven GCaMP6m reporter. All measures of cortical network activity and synchrony were compared to baseline measures from neurons cocultured with nai¨ve astrocytes. RESULTS: Cortical networks containing astrocytes previously exposed to serum exhibit hypersynchrony and increased network bursting when exposed to the inflammatory cytokine, IFNG. Importantly, this seizure-like response to IFNG does not occur when cortical networks contain astrocytes that have never been exposed to serum. Moreover, the developmental timing and frequency of cortical network bursting are consistent with Giant Depolarizing Potentials (GDPs), which are GABA-driven and thus refractory to most anti-seizure medications. CONCLUSIONS: Taken together, our results indicate a novel mechanism by which an intracranial hemorrhage that exposes astrocytes to serum can predispose cortical networks to exhibit medically refractory, seizure-like activity in response to an immune-activating event later in life.