[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.


CONCLUSIONS
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.
Wang
X
X
Toxicology Institute, Nanjing Medical University, Nanjing 210029, China.
Xiao
H
H
Dai
X
X
Liu
X
X
Yu
X
X
Wu
J
J
D000818:Animals; D004347:Drug Interactions; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism*; D007306:Insecticides / Q000633:toxicity*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009570:Nitriles; D009946:Organothiophosphorus Compounds / Q000633:toxicity*; D018408:Patch-Clamp Techniques; D011722:Pyrethrins / Q000633:toxicity*; D051381:Rats; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology*
D007306:Insecticides; D009570:Nitriles; D009946:Organothiophosphorus Compounds; D011722:Pyrethrins; D015222:Sodium Channels; D013779:Tetrodotoxin; C003135:phoxim; C017690:fenvalerate