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Neurobiol Dis. 2016 Jan;85:111-121. doi: 10.1016/j.nbd.2015.10.019. Epub 2015 Oct 22.

Soluble Aβ oligomers impair hippocampal LTP by disrupting glutamatergic/GABAergic balance.

Author information

1
Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA; Department of Neurology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080, China.
2
Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
3
Department of Neurology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou 510080, China; Department of Neurology, The First Affiliated Hospital of Guangzhou Medical University, Guangdong 510120, China. Electronic address: pingyixu@sina.com.
4
Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA. Electronic address: sli11@partners.org.

Abstract

Epileptic activity may be more prevalent in early stage Alzheimer's disease (AD) than previously believed. Several studies report spontaneous seizures and interictal discharges in mouse models of AD undergoing age-related Aβ accumulation. The mechanism by which Aβ-induced neuronal excitability can trigger epileptiform activity remains unknown. Here, we systematically examined field excitatory postsynaptic potentials (fEPSP) in stratum radiatum and population spikes (PSs) in the adjacent stratum pyramidale of CA1 in wild-type mouse hippocampal slices. Soluble Aβ oligomers (oAβ) blocked hippocampal LTP and EPSP-spike (E-S) potentiation, and these effects were occluded by prior treatment with the glutamate uptake inhibitor TBOA. In accord, oAβ elevated glutamate levels in the hippocampal slice medium. Recording the PS revealed that oAβ increased PS frequency and reduced LTP, and this LTP deficit was occluded by pretreatment with the GABAA antagonist picrotoxin. Whole-cell recordings showed that oAβ significantly increased spontaneous EPSC frequency. Decreasing neuronal activity by increasing GABA tone or partially blocking NMDAR activity prevented oAβ impairment of hippocampal LTP. Finally, treating slices with two antiepileptic drugs rescued the LTP inhibition induced by oAβ. We conclude that soluble Aβ oligomers at the low nanomolar levels present in AD brain increase neuronal excitability by disrupting glutamatergic/GABAergic balance, thereby impairing synaptic plasticity.

KEYWORDS:

Alzheimer's disease; Aβ oligomers; Epileptiform activity; Longterm potentiation; Population spike; Synaptic plasticity

PMID:
26525100
PMCID:
PMC4778388
DOI:
10.1016/j.nbd.2015.10.019
[Indexed for MEDLINE]
Free PMC Article

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