Amyloid β-Induced Neuronal Hyperexcitability Triggers Progressive Epilepsy
Open Access
- 18 March 2009
- journal article
- research article
- Published by Society for Neuroscience in Journal of Neuroscience
- Vol. 29 (11), 3453-3462
- https://doi.org/10.1523/jneurosci.5215-08.2009
Abstract
Alzheimer's disease is associated with an increased risk of unprovoked seizures. However, the underlying mechanisms of seizure induction remain elusive. Here, we performed video-EEG recordings in mice carrying mutant humanAPPsweandPS1dE9genes (APdE9mice) and their wild-type littermates to determine the prevalence of unprovoked seizures. In two recording episodes at the onset of amyloid β (Aβ) pathogenesis (3 and 4.5 months of age), at least one unprovoked seizure was detected in 65% ofAPdE9mice, of which 46% had multiple seizures and 38% had a generalized seizure. None of the wild-type mice had seizures. In a subset ofAPdE9mice, seizure phenotype was associated with a loss of calbindin-D28k immunoreactivity in dentate granular cells and ectopic expression of neuropeptide Y in mossy fibers. InAPdE9mice, persistently decreased resting membrane potential in neocortical layer 2/3 pyramidal cells and dentate granule cells underpinned increased network excitability as identified by patch-clamp electrophysiology. At stimulus strengths evoking single-component EPSPs in wild-type littermates,APdE9mice exhibited decreased action potential threshold and burst firing of pyramidal cells. Bath application (1 h) of Aβ1–42 or Aβ25–35 (proto-)fibrils but not oligomers induced significant membrane depolarization of pyramidal cells and increased the activity of excitatory cell populations as measured by extracellular field recordings in the juvenile rodent brain, confirming the pathogenic significance of bath-applied Aβ (proto-)fibrils. Overall, these data identify fibrillar Aβ as a pathogenic entity powerfully altering neuronal membrane properties such that hyperexcitability of pyramidal cells culminates in epileptiform activity.Keywords
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