Contribution Of Early Alzheimer'S Disease-Related Pathophysiology To The Development Of Acquired Epilepsy

Aberrant epileptic activity is detectable at early disease stages in Alzheimer's disease (AD) patients and in AD mouse models. Here, we investigated in young ArcticA mice whether AD-like pathology renders neuronal networks more susceptible to the development of acquired epilepsy induced by unilateral intrahippocampal injection of kainic acid (IHK). In this temporal lobe epilepsy model, IHK induces a status epilepticus followed after two weeks by spontaneous recurrent seizures (SRS). ArcticA mice exhibited more severe status epilepticus and early onset of SRS. This hyperexcitable phenotype was characterized in CA1 neurons by decreased synaptic strength, increased kainic acid-induced LTP and reduced frequency of spontaneous inhibitory currents. However, no difference in neurodegeneration, neuroinflammation, axonal reorganization or adult neurogenesis was observed in ArcticA mice compared to wild-type littermates following IHK-induced epileptogenesis. Neuropeptide Y (NPY) expression was reduced at baseline and its IHK-induced elevation in mossy fibres and granule cells was attenuated. However, although this alteration might underlie premature seizure onset, neutralization of soluble A species by intracerebroventricular A-specific antibody application mitigated the hyperexcitable phenotype of ArcticA mice and prevented early SRS onset. Therefore, the development of seizures at early stages of AD is mediated primarily by A species causing widespread changes in synaptic function.