Effects of sodium metabisulfite on sodium current in acutely isolated rat hippocampal CA1 neurons

AIM: To study the effects of sodium metabisulfite (SMB), sulfur dioxide (SO2) and its derivatives in vivo, sodium bisulfite and sulfite, on Na+ currents. The effects of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) against SMB were also studied in freshly dissociated hippocampal CA1 neurons in rats. METHODS: The whole-cell patch-clamp techniques were used in the experiments. RESULTS: ① SMB increased the voltage-activated Na+ currents in a concentration-and voltage-dependent manner. The amplitudes of Na+ currents was increased (22.36±3.28) % and (65.05±5.75)% (n=10) by SMB at 2 μmol/L and 20 μmol/L, respectively. ② SMB (10 μmol/L) did not affect the activation process, but changed the inactivation process significantly. Before and after application of 10 μmol/L SMB, the half-inactivation voltage was (-82.38±0.54) mV and (-69.39±0.41) mV (n=10, P<0.01). However, the slope factor remained unchanged. ③ SOD, CAT and GPx partly inhibited the incremental effect of SMB on Na+ currents. CONCLUSION: SMB increases Na+ currents and inhibits the steady-state inactivation, which contributes to the increase in the excitibility of neuronal cells. Its mechanism may involve oxidative damage caused by sulfur-and oxygen-centered free radicals in the rat hippocampal CA1 neurons.