Effects of SO2 derivatives on sodium currents in acutely isolated rat hippocampal lead-exposed neurons

In this study, the effects of acute SO₂ derivatives and chronic lead exposure together on sodium cur-rents (I_Na) were investigated in acutely isolated rat hippocampal neurons by using the whole-cell patch clamp techniques. We found that chronic lead exposure hardly reduced the amplitudes of I_Na. In the normal condition, sodium current started to appear at around -70 mV, and reached the peak current at around -40 mV. After chronic lead exposure, the data changed to -70 and -30 mV. After adding SO₂ derivatives, the data changed to -80 and -40 mV, respectively. SO₂ derivatives caused a significant in-crease of INa in hippocampal chronic-lead exposed neurons. Chronic lead exposure induced a right shift of the activation curve and a left shift of the inactivation curve of sodium channels. SO₂ derivatives caused negative shifts of the activation and inactivation curves of I_Na in hippocampal chronic-lead ex-posed neurons. Lead exposure put off the time reaching the peak of I_Na activation. SO₂ derivatives in-creased the time constants of inactivation after lead exposure. The interaction of lead and SO₂ deriva-tives with voltage-dependent sodium channels may lead to changes in electrical activity and contribute to worsening the neurotoxicological damage.