Effects of Sodium Metabisulfite on Sodium Currents in Rat Dorsal Root Ganglion Neurons

Effects of sodium metabisulfite(SMB),a food preservative,on tetrodotoxin-sensitive(TTX-S) and tetrodotoxin-resistant(TTX-R) sodium channels in cultured post-natal dorsal root ganglion(DRG) neurons were studied using the whole cell configuration of patch-clamp technique.The results showed SMB increased the sodium currents of TTX-S and TTX-R in a concentration-and voltage-dependent manner.10 μmol/L SMB did not affect the activation process of TTX-S,the half-activation voltages of TTX-S were(-28.06 ± 1.30) and(-29.92 ± 1.42) mV(n = 8,P0.05) before and after application of 10 μmol/L SMB,respectively,and their slope factors were not changed.But the inactivation curve of TTX-S was shifted to positive potentials,the half-inactivation voltages of TTX-S were(-71.33 ± 0.87) and(-57.88 ± 0.98) mV(n = 8,P0.01) before and after application of SMB(10 μmol/L),respectively,without changing the slope factors.5 μmol/L SMB affected the activation and inactivation process of TTX-R.Before and after application of 5 μmol/L SMB,the half-activation voltages of TTX-R were(-10.44 ± 0.62) and(-16.62 ± 0.82) mV(n = 8,P0.01),respectively,the half-inactivation voltages of TTX-R were(-33.39 ± 0.38) and(-40.94 ± 0.60) mV(n = 8,P0.01),respectively,and their slope factors were not changed.These results lead the conclusions: SMB significantly increased the sodium currents of TTX-S and TTX-R in rat DRG neurons.SMB shifted the steady-state activation curve of TTX-R to more negative potentials and inhibited their inactivation process of TTX-S and TTX-R,and excitability of the neurons was increased by SMB.It implies that there are physiological modulation and pathophysiologic effects of sulfur dioxide and its derivative bisulfite on rat dorsal root ganglion neurons.