氰戊菊酯和辛硫磷对大鼠背根节细胞钠通道的影响

目的　观察氰戊菊酯、辛硫磷农药单用和混用对成年大鼠背根神经节 (DRG)神经元钠通道的毒性作用。方法　应用膜片钳技术研究氰戊菊酯和辛硫磷对DRG河豚毒素敏感 (TTX S)和不敏感 (TTX R)型钠通道的作用。结果　氰戊菊酯明显延迟去极化时TTX R型钠通道的关闭时间 ,氰戊菊酯 10、5 0、10 0 μmol/L组和对照组钠通道峰电流失活时间常数分别为 (8 10± 2 41)ms、(11 78±2 76 )ms、(8 76± 1 94)ms和 (6 41± 1 32 )ms。氰戊菊酯还具有延长TTX R型钠通道尾电流的关闭时间 ,氰戊菊酯 10、5 0、10 0 μmol/L组和对照组尾电流失活时间常数分别为 (6 11± 0 5 2 )ms、(7 82±0 82 )ms、(7 2 3± 1 0 9)ms和 (4 91± 0 97)ms。氰戊菊酯对TTX S型钠通道的作用小于TTX R型 ,仅表现为对尾电流的关闭有延迟作用。辛硫磷对这两种亚型钠通道无明显影响 ,将氰戊菊酯和辛硫磷混配使用后 ,仅见氰戊菊酯作用的表现 ,未见氰戊菊酯和辛硫磷的联合作用。结论　氰戊菊酯影响DRG钠通道峰电流和尾电流 ,对TTX R型钠通道的作用大于TTX S型 ,未见氰戊菊酯和辛硫磷混配对钠通道的联合作用

Effects of phoxim and fenvalerate on TTX-S and TTX-R sodium channels in the DRG neurons of adult rat

OBJECTIVE: To study the joint neurotoxic effects of phoxim (Pho) and fenvalerate (Fen) on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) Na(+) currents in dorsal root ganglion (DRG) neurons of adult rat. METHODS: Whole cell patch clamp technique was used to test the effects of Pho and Fen on TTX-S and TTX-R sodium currents in DRG neurons. RESULTS: The inactivation of TTX-R sodium channel was obviously slowed down by Fen. The tau(Na) of peak currents at doses of 10, 50 and 100 micromol/L Fen and control groups were (8.10 +/- 2.41) ms, (11.78 +/- 2.76) ms, P < 0.01, (8.76 +/-1.94) ms, P < 0.05 and (6.41 +/- 1.32) ms respectively. The inactivation of TTX-R sodium channel tail currents was also significantly delayed by Fen. The tau(Na) of the tail currents at doses of 10, 50, 100 micromol/L Fen and control groups were 6.11 +/- 0.52 (P < 0.05), 7.82 +/- 0.82 (P < 0.05), 7.23 +/- 1.09 (P < 0.05) and (4.91 +/- 0.97) ms separately. As compared with TTX-R sodium channel, the TTX-S sodium channel was less responsive to Fen exposure, which only led to slowly decay TTX-S sodium tail currents. There was no any effect of Pho on the TTX-S and TTX-R sodium channels. The mixed treatment of a Pho and Fen did not show joint effect on the sodium currents. CONCLUSION: Both the peak and tail currents are changed by Fen, however, Fen has more remarkable effects on TTX-R than on TTX-S sodium channel. The combined exposure to Pho and Fen shows no joint effect on the sodium channel.