Widespread neuronal injury in a model of cholinergic status epilepticus in postnatal day 7 rat pups

• Cholinergic status epilepticus was induced with high-dose lithium and pilocarpine in postnatal day 7 rat pups.
• EEGs showed continuous polyspikes activity for 54.3 ± 6.7 min, while O2 saturation showed no significant hypoxemia.
• Widespread neuronal injury (fluoro-jade B staining) and increase in caspase-3a IR were observed by 24 h after SE onset.
• Caspase-3a-IR neurons had fragmented nuclei, suggesting that SE triggered an irreversible form of cell injury.

ObjectiveStatus Epilepticus (SE) is common in neonates and infants, and is associated with neuronal injury and adverse developmental outcomes. However, the role of SE in this injury is uncertain. Until now, we have lacked an animal model in which seizures result in neuronal injury in rodent models at ages below postnatal day 12 (P12) unless seizures are combined with inflammatory stressors.MethodsWe induced SE with high-dose lithium and pilocarpine in P7 rats, which are developmentally close to human neonates. Several EEG measures and O2 saturation were recorded during the 6 h following initiation of SE. We assessed neuronal injury at 6 and 24 h post-SE onset using Fluoro–Jade B staining (FJB) and caspase-3a immunoreactivity (IR).ResultsEEGs showed continuous polyspikes activity for 54.3 ± 6.7 min, while O2 saturation showed no significant hypoxemia. By 24 h after SE onset, significant neuronal injury was observed in CA1/subiculum, CA3, dentate gyrus, thalamus, neocortex, amygdala, piriform cortex, lateral entorhinal cortex, hypothalamus, caudate putamen, globus pallidus, ventral pallidum, and nucleus accumbens. At 24 h post-SE, caspase-3a IR was significantly increased in CA1/subiculum, thalamus, and neocortex compared to sham, and caspase-3a IR neurons had fragmented nuclei, suggesting that SE triggered an irreversible form of cell injury.SignificanceIn conclusion, we have developed a model of cholinergic SE in P7 rat pups, which combines high survival (69.9% survival at 24 h) and widespread brain injury. These studies suggest that the immature brain is vulnerable to severe forms of SE.