Abstract:

Among the many biological effects caused by low intensity extremely high frequency electromagnetic fields (EHF-EMF) reported in the literature, those on the nervous system are a promising area for further research. The mechanisms by which these fields alter neural activity are still unclear and thus far there appears to be no frequency dependence regarding neuronal responses. Therefore, proper in vitro models for preliminary screening studies of the interaction between neural cells with EMF are needed. We designed an artificial axon model consisting of a series of parallel RC networks. Each RC network contained an aqueous solution of lipid vesicles with a gradient of potassium (K⁺) concentration as the functional element. We investigated the effects of EHF-EMF (53.37 GHz–39 mW) on the propagation of the electric impulse. We report that exposure to the EHF-EMF increases the amplitude of electrical signal by inducing a potassium efflux from lipid vesicles. Further, exposure to the EHF-EMF potentiates the action of valinomycin – a K⁺ carrier – increasing the extent of K⁺ transport across the lipid membrane. We conclude that exposure to the EHF-EMF facilitates the electrical signal propagation by increasing transmembrane potassium efflux, and that the model presented is promising for future screening studies of different EMF frequency spectrum bands.

Excerpts:

it has been found that the lateral pressure dynamics of the membrane is significantly influenced by EHF-EMF²⁸, and that this membrane property is highly sensitive to even small changes in membrane composition. Further, direct effects of EHF-EMF on the voltage-sensitive channels in the neuronal plasma membrane⁷ and an increase in permeability due to rearrangement of membrane phospholipids structure have been indicated²⁹.we conclude that EHF-EMF is very effective in altering the membrane structure (increasing K⁺ permeability), although a description of its action at the molecular or supramolecular levels remains elusive. In particular, potentially synergistic effects related to membrane organization and pore-forming peptide/proteins should be carefully looked into in the future.

Although sample heating is the most widely accepted mechanism of high frequency EMF interaction in biological systems, in our case we can safely hypothesize that the observed effects were mediated through non-thermal mechanisms (Figs 5 and 6). Recently, similar mechanisms were proposed as an explanation of the effects of low intensity EHF-EMF on nervous tissue involving a direct interaction with the neuronal plasma membrane⁷. Further non-thermal mechanisms were also suggested to explain the transient response of high frequency EMF on the electrical activity of the sural nerve in vivo, which appears to be specific to the field because the radiant heating did not reproduce this effect³⁴. Thus our results suggest subtle specific effects, which do not depend on the thermal energy imparted by the EHF-EMF on the axon model.

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