Exposure to 50??Hz electromagnetic field changes the efficiency of the scorpion alpha toxin

摘要

class="Heading">Background id="Par1" class="Para">Extremely low-frequency (50??Hz) electromagnetic field (ELF-EMF) is produced by electric power transmission lines and electronic devices of everyday use. Some phenomena are proposed as a€?first effectsa€? of ELF-EMF: the discrete changes in the membrane potential and the increase of the calcium channel activity as well as the intracellular concentration of Ca2+. Interaction of the scorpion alpha toxin with the sodium channel depends on the orientation of the charges and may be perturbed by changes in the membrane polarization. The toxin induces overexcitability in the nervous system and an increase in the neurotransmitters released with different consequences, mainly the paralysis of muscles. We assumed that the exposure to ELF-EMF 0.7 mT will change the effects of the insect selective scorpion alpha toxin (recombinant Lqh?±IT from Leiurus quinquestriatus hebraeus) at the level of the cercal nerve function, the synaptic transmission and on the level of entire insect organism. Taking into account the compensatory mechanisms in organisms, we tested in addition ten times higher ELF-EMF on whole insects. class="Heading">Methods id="Par2" class="Para">Experiments were performed in vivo on cockroaches (Periplaneta americana) and in vitro - on isolated cockroach abdominal nerve cord with cerci. In biotests, the effects of Lqh?±IT (10a?’8 M) were estimated on the basis of the insect ability to turn back from dorsal to ventral side. Three groups were compared: the control one and the two exposed to ELF-EMF - 0.7 and 7 mT. Bioelectrical activity of the cercal nerve and of the connective nerve that leaves the terminal abdominal ganglion was recorded using extracellular electrodes. Lqh?±IT (5a€‰?—a€‰10a?’8 M) induced modifications of neuronal activity that were observed in the control cockroach preparations and in the ones exposed to ELF-EMF (0.7 mT). The exposure to ELF-EMF was carried out using coils with a size appropriate to the examined objects. class="Heading">Results id="Par3" class="Para">The exposure to ELF-EMF (0.7 mT) modified the effects of Lqh?±IT (5a€‰?—a€‰10a?’8 M) on activity of the cercal nerve and of the connective nerve. We observed a decrease of the toxin effect on the cercal nerve activity, but the toxic effect of Lqh?±IT on the connective nerve was increased. Biotests showed that toxicity of Lqh?±IT (10a?’8 M) on cockroaches was reduced by the exposure to ELF-EMF (0.7 and 7 mT). class="Heading">Conclusions id="Par4" class="Para">The exposure to 50??Hz ELF-EMF modified the mode of action of the anti-insect scorpion alpha toxin Lqh?±IT at cellular level of the cockroach nervous system and in biotests. Toxin appeared as a usefull tool in distinguishing between the primary and the secondary effects of ELF-EMF.