Inhibition of Sodium Channels in Rat Dorsal
Root Ganglion Neurons by
Hainantoxin-IV, a Novel Spider Toxin
XIAO Yu-Cheng, LIANG Song-Ping*
( College of Life
Sciences, Hunan Normal University, Changsha 410081, China )
Abstract
The effects of Hainantoxin-IV (HNTX-IV), a neurotoxic peptide isolated from the venom
of the Chinese bird spider Seleconosmia hainana, on the adult rat dorsal root ganglion (DRG)
neurons were investigated. Using the whole-cell patch-clamp technique HNTX-IV inhibited mammal neural
TTX-sensitive (TTX-S) sodium currents evidently but the toxin failed to affect TTX-resistant (TTX-R)
ones. The inhibition of HNTX-IV is dose-dependent with the IC
toxin didn’t affect the activation and inactivation kinetics of sodium currents, but it caused a 10.1
mV hyperpolarizing shift in the voltage midpoint of steady-state sodium channel inactivation on DRG
neurons. The results indicated that HNTX-IV, a novel spider toxin, maybe alternate voltage-gated sodium
channels through a mechanism distinct from other spider toxins such as &dgr;-ACTXs, &mgr;-agatoxins
I-VI which targeted the receptor site 3 to slow the inactivation kinetics of sodium currents.
Key
words spider toxin; dorsal ganglion neurons; sodium current;
whole-cell patch-clamp
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