BACKGROUND AND AIMS: Extremely low-frequency (50 Hz) electromagnetic field (ELF-EMF) is produced by electrical appliances and electric power transmission lines. It affects organism functions and induces among others: the discrete changes in neuronal membrane potential, the increase of calcium channel activity and intracellular concentration of Ca2+. In insects, ELF-EMF causes an increase in a level of stress hormone – the octopamine. Site-3 ligands of voltage-dependent sodium channel inhibit fast inactivation of the channel. Receptor site-3 is located in the immediate vicinity of voltage sensor of the sodium channel. The LqhαIT toxin from the scorpion Leiurus quinquestriatus venom is an example of a site-3 ligand. The aim of our study was to investigate whether ELF-EMF exposure affects the action of the LqhαIT toxin on an axonal membrane. METHODS: We have observed an action of 0.7 mT ELF-EMF and LqhaIT (5×10-8 M) on the bioelectrical activity of an isolated nerve cord of the cockroach – Periplaneta americana. The tests have been conducted using extracellular electrodes, which allowed to record the total bioelectric activity from one connective and one cercal nerve. Additionally, we have performed in-vivo tests, during which we have estimated the impact of 0.7 mT and 7 mT ELF-EMF on the degree of the insect paralysis caused by the LqhαIT (10-8 M and 10-7 M). RESULTS: ELF-EMF exposure induced important changes in the LqhαIT activity – much higher during synaptic transmission than on a level of “cable transmission”. In-vivo, electromagnetic field probably accelerates the insect detoxification process because paralysis induced by the toxin was much lower after the exposure than in control. CONCLUSION: Results of our experiments can suggest the changes in organism sensitivity to neurotoxic ligands.
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