Stress-Reducing Effect of a 50 Hz Electric Field in Mice after Repeated Immobilizations, Electric Field Shields, and Polarization of the Electrodes

SIMPLE SUMMARY: With the increasing demand for electricity and electrical equipment, humans are routinely and unintentionally exposed to electric fields (EFs). Although no considerable adverse effects of EF exposure have been observed, slight physiological effects are known to occur. Additionally, there are methods and devices that expose subjects to EF for medical purposes. The mechanism of the biological effects of EF has not been identified, because the effects are not strong and may involve the physical properties of EFs, which are invisible and easily disturbed by obstacles. In a simple and short experiment using mice, we found that EF has an inhibitory effect on glucocorticoid (GC) responses. The experiment’s reproducibility was almost 100%. We tried to improve the understanding of the biological effects of EF by structuring our observations of the stress-reducing effects under different conditions in the system. We found that the inhibitory effect on the GC response was attenuated by EF shielding. We compared the effects of EF shielding between the head and abdomen, and found that the effects of EF were attenuated in both conditions, but might be more attenuated when the head was shielded. Thus, it appears that the area where the EF is distributed and the body part are important for the biological effects of EF. Two experiments with different conditions were performed. These results will help advance the current understanding of the effects of EF on stress systems. ABSTRACT: In BALB/c mice, immobilization-increased plasma glucocorticoid (GC) levels are suppressed by extremely low frequency (ELF) electric fields (EF). The aim of this study was to advance our understanding of the biological effects of ELF-EF, using its suppressive effect on the GC response. Mice were exposed to a 50 Hz EF of 10 kV/m via a parallel plate electrode and immobilized as needed. We examined the suppressive effect of ELF-EF on GC level change after repeated immobilizations, electrode polarization, and EF shielding of different portions of the mouse body parts. Additionally, bodyweight changes owing to stress and EF were examined. Immobilization-induced reduction in the plasma GC levels was reproduced in mice with stress and EF exposure, regardless of the stress episode numbers and electrode polarization. Furthermore, when the head of mice was shielded from the EF, the suppressive effect was possibly relatively lower than that when the abdomen was shielded. The bodyweight of the mice decreased for 3 days after immobilization before recovering; ELF-EF did not affect the bodyweight. Thus, to elicit the biological effects of the EF, not only the size of the area where the EF is distributed but also the area where the field is distributed should be important. The results also confirmed the stableness of the present experimental system, at least in terms of the stress-reducing effect. In addition, the restriction in this study caused weight loss, but ELF-EF was not considered to affect it. The results improve the understanding of the biological effect and medical applications of ELF-EF.