Nicholson G M, Little M J, Tyler M, Narahashi T
Department of Health Sciences, University of Technology, Sydney, NSW, Australia.
Toxicon. 1996 Nov-Dec;34(11-12):1443-53. doi: 10.1016/s0041-0101(96)00089-x.
The actions of potent mammalian neurotoxins isolated from the venom of two Australian funnel-web spiders were investigated using both electrophysiological and neurochemical techniques. Whole-cell patch clamp recording of sodium currents in rat dorsal root ganglion neurons revealed that versutoxin (VTX), isolated from the venom of Hadronyche versuta, produced a concentration-dependent slowing or removal of tetrodotoxin-sensitive (TTX-S) sodium current inactivation and a reduction in peak TTX-S sodium current. In contrast, VTX had no effect on tetrodotoxin-resistant (TTX-R) sodium currents or potassium currents. VTX also shifted the voltage dependence of sodium channel activation in the hyperpolarizing direction and increased the rate of recovery from inactivation. Ion flux studies performed in rat brain synaptosomes also revealed that robustoxin (RTX), from the venom of Atrax robustus, and VTX both produced a partial activation of 22Na+ flux and an inhibition of batrachotoxin-activated 22Na+ flux. This inhibition of flux through batrachotoxin-activated channels was not due to an interaction with neurotoxin receptor site 1 since [3H]saxitoxin binding was unaffected. In addition, the partial activation of 22Na+ flux was not enhanced in the presence of alpha-scorpion toxin and further experiments suggest that VTX also enhances [3H]batrachotoxin binding. These selective actions of funnel-web spider toxins on sodium channel function are comparable to those of alpha-scorpion and sea anemone toxins which bind to neurotoxin receptor site 3 on the channel to slow channel inactivation profoundly. Also, these modifications of sodium channel gating and kinetics are consistent with actions of the spider toxins to produce repetitive firing of action potentials.
运用电生理学和神经化学技术，对从两种澳大利亚漏斗网蜘蛛毒液中分离出的强效哺乳动物神经毒素的作用进行了研究。在大鼠背根神经节神经元中对钠电流进行全细胞膜片钳记录发现，从哈氏漏斗蛛毒液中分离出的强效毒素（VTX）可产生浓度依赖性的河豚毒素敏感性（TTX-S）钠电流失活减慢或消除，以及TTX-S钠电流峰值降低。相比之下，VTX对河豚毒素抗性（TTX-R）钠电流或钾电流没有影响。VTX还使钠通道激活的电压依赖性向超极化方向偏移，并增加了从失活状态恢复的速率。在大鼠脑突触体中进行的离子通量研究还表明，来自粗壮漏斗蛛毒液的强劲毒素（RTX）和VTX均能部分激活22Na+通量，并抑制蛙毒素激活的22Na+通量。这种对通过蛙毒素激活通道的通量的抑制并非由于与神经毒素受体位点1相互作用，因为[3H]石房蛤毒素结合不受影响。此外，在存在α-蝎毒素的情况下，22Na+通量的部分激活并未增强，进一步的实验表明VTX还能增强[3H]蛙毒素结合。漏斗网蜘蛛毒素对钠通道功能的这些选择性作用与α-蝎毒素和海葵毒素相当，它们与通道上的神经毒素受体位点3结合，从而显著减慢通道失活。同样，这些对钠通道门控和动力学的改变与蜘蛛毒素产生动作电位重复发放的作用一致。
