Persistent sodium currents contribute to Aβ1-42-induced hyperexcitation of hippocampal CA1 pyramidal neurons

Patients with Alzheimer's disease (AD) have elevated incidence of epilepsy. Moreover, neuronal hyperexcitation occurs in transgenic mouse models overexpressing amyloid precursor protein and its pathogenic product, amyloid beta protein (A beta). However, the cellular mechanisms of how A beta causes neuronal hyperexcitation are largely unknown. We hypothesize that the persistent sodium current (I-NaP), a subthreshold sodium current that can increase neuronal excitability, may in part account for the A beta-induced neuronal hyperexcitation. The present study was designed to evaluate the involvement of I-NaP in A beta-induced hyperexcitation of hippocampal CA1 pyramidal neurons using a whole-cell patch-clamp recording technique. Our results showed that bath application of soluble A beta(1-42) increased neuronal excitability in a concentration-dependent manner. Soluble A beta(1-42) also increased the amplitude of I-NaP without significantly affecting its activation properties. In the presence of riluzole (RLZ), an antagonist of I-NaP, the A beta(1-42)-induced neuronal hyperexcitation and I-NaP augmentation were significantly inhibited. These findings suggest that soluble A beta(1-42) may induce neuronal hyperexcitation by increasing the amplitude of I-NaP and that RLZ can inhibit the A beta(1-42)-induced abnormal neuronal activity. (C) 2014 Elsevier Ireland Ltd. All rights reserved.