In one part of the experiment, the whole body exposure of rats was performed (11 rats in the 60 h exposure group, 10 rats in the 15 h exposure group and 10 rats in sham exposure group) and brain slices prepared from the previously treated animals were investigated. In the other part of the study, neocortical and hippocampal slices of 11 untreated rats were directly exposed following the dissection. The electromagnetic field intensities (250-500 mT, 50 Hz) were chosen on the basis of the literature, according to the reference level for occupational exposure (ICNIRP-guideline 1998).
Altogether 55 neocortical and 31 hippocampal slices were tested.
Exposure duration: continuous for 15 h/day on 1 day or 4 consecutive days
Exposure duration: continuous for 1 h
|Helmholtz coil apparatus consisting of two solenoids with a radius of 21 cm each, 21 cm apart; coils constructed of 240 turns of glaze-insulated copper wire (d=1.4 mm); rats placed in 35 cm x 35 cm x 17 cm opaque plastic boxes in the center of the coils
|A sham exposure was conducted.
|magnetic flux density
The most pronounced effect was a decrease in basic synaptic activity in the slices exposed directly ex vivo observed as a diminution in amplitude of evoked potentials. On the other hand, following whole body exposure of the rats an enhanced short- and long-term synaptic facilitation in hippocampal slices and an increased seizure susceptibility in neocortical slices was found (opposite effect compared to ex vivo exposure). However, these effects seem to be transient.
The authors conclude that extremely low frequency electromagnetic field exposure exerts significant effects on synaptic activity, but the overall changes may strongly depend on the synaptic structure and neuronal network of the affected region together with the specific spatial parameters and constancy of electromagnetic field exposure.