Hydrogen peroxide modulates K+ ion currents in cultured Aplysia sensory neurons

Hydrogen peroxide (H2O2) causes oxidative stress and is considered a mediator of cell death in various organisms. Our previous studies showed that prolonged (> 6 h) treatment of Aplysia sensory neurons with I mM H2O2 produced hyperpolarization of the resting membrane potential, followed by apoptotic morphological changes. In this study, we examined the effect of H2O2 on the membrane conductance of Aplysia sensory neurons. Hyperpolarization was induced by 10 mM H2O2 within I h, and this was attributed to increased membrane conductance. In addition, treatment with 10 mM H2O2 for 3 min produced immediate depolarization, which was due to decreased membrane conductance. The H2O2-induced hyperpolarization and depolarization were completely blocked by dithiothreitol, a disulfide-reducing agent. The later increase of membrane conductance induced by H2O2 was completely blocked by 100 MM TEA, a K+ channel blocker, suggesting that H2O2-induced hyperpolarization is due to the activation of K+ conductance. However, the inhibition of K+ efflux by TEA did not protect against H2O2-induced cell death in cultured Aplysia sensory neurons, which indicates that the signal pathway leading to H2O2-induced cell death is more complicated than expected. (C) 2003 Elsevier Science B.V. All rights reserved.