β-Amyloid peptide (Aβ) is known to be involved in Alzheimer's disease (AD). Although the fibril form of Aβ is known to have neurotoxicity, it has been shown that not only the fibril form but also the oligomer form of Aβ may be related to the neuropathophysiology of AD, specifically to memory loss. Some studies have demonstrated that low concentrations of the Aβ oligomer impair long-term potentiation (LTP), a cellular model for learning and memory, after short exposure times in vivo and in vitro, although little is known about the mechanism involved in Aβ-mediated inhibition of LTP. In this study, we used the patch clamp whole-cell technique in rat hippocampal CA1 pyramidal neurons to study more precisely how the Aβ oligomer affects synaptic plasticity. The brief perfusion of slices with a low concentration (1 μM) of Aβ1-42 significantly impaired LTP induction of the excitatory input. The same concentration of Aβ did not affect basal transmission or paired-pulse facilitation. We also demonstrated that neither NMDAR-EPSCs nor the voltage-depended calcium channel (VDCC) currents were affected by the same concentration of Aβ1-42 as used in the LTP experiments. These data suggest that Aβ mediated impairment of LTP induction is independent of NMDARs or VDCCs.
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