Modulation of tetrodotoxin-resistant sodium channels by dihydropyrazole insecticide RH-3421 in rat dorsal root ganglion neurons |
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Authors: | Tsurubuchi Y Zhao X Nagata K Kono Y Nishimura K Yeh J Z Narahashi T |
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Affiliation: | Institute of Agriculture and Forestry, University of Tsukuba, Japan. |
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Abstract: | The effects of the dihydropyrazole insecticide RH-3421 on the retrodotoxin-resistant (TTX-R) voltage-gated sodium channels in rat dorsal root ganglion (DRG) neurons were studied using the whole-cell patch clamp technique. RH-3421 at 10 nM to 1 microM completely blocked action potentials. The sodium currents were irreversibly suppressed by 1 microM RH-3421 in a time- and a dose-dependent manner and the IC50 value of RH-3421 was estimated to be 0.7 microM after 10 min of application. RH-3421 blocked the sodium currents to the same extent over the entire range of test potentials. The sodium conductance-voltage curve was not shifted along the voltage axis by 1 microM RH-3421 application In contrast, both fast and slow steady-state sodium channel inactivation curves were shifted in the hyperpolarizing direction in the presence of 1 microM RH-3421. It was concluded that RH-3421 bound to the resting and inactivated sodium channels to cause block with a higher affinity for the latter state. |
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Keywords: | Sodium channel Dihydropyrazole RH-3421 Tetrodotoxin-resistant sodium channel Dorsal root ganglion |
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