the effects of two isolated fractions from buthotusschach scorpion venom on action potential properties in snail neurons

abstract background: understanding the electrophysiological effects of toxins, may facilitate new drugs discovery. buthotusschach (bs) has been shown to be one of the most dangerous scorpions in tropical part of iran. present study was aimed to investigate the electrophysiological effects of two active fractions (f4 and f6) isolated from bs scorpion toxin on action potential (ap) characteristics of snail neurons. materials and methods: intracellular recording was made from f1 cells of helix aspersa in the presence and absence of extracellular application of f4 and f6fractions (50nm and1µm) isolated from bs scorpion venom. results: in control condition, the resting membrane of neurons (rmp) -43.11±0.33mv,the ap amplitude was 49.34±0.39mv and the time to peak of ap was 17.02±0.32ms. while addition of f4 fraction to the bathing solution had a dual effects on membrane potential in a voltage dependent manner. therefore,it caused membrane hyperpolarization at 50nm (-48.81±0.54mv p<0.001), but its 1µm concentration shifted the membrane potential towards depolarized voltages (-40.35±0.25 mv p<0.001).. the amplitude of ap was significantly decreased only by low dose of f4 fraction (45.38±0.46mv p<0.001).the time to peak was significantly (p≤0.001) increased by both concentrations of f4 fraction. while f6 fraction made the rmp more depolarized. in addition, ringer containing 50nm of f6 fraction led to a significant increase in the amplitude (52.27±0.39 mv p<0.001) and the time to peak of ap (28.04±0.92ms, p<0.001),whereas at higher concentration had no significant effect on these parameters. conclusion: f4 and f6 fractions caused changes in the ap characteristics, which based on the role of sodium channels in the amplitude and the time to peak it seems these fractions possibly changes the aforementioned parameters through effects on sodium channels. keywords: scorpion toxin, intracellular recording, action potential, buthotusschach.