Characterization of the suppressive effects of extremely-low-frequency electric fields on a stress-induced increase in the plasma glucocorticoid level in mice.

We recently suggested that an increase in the plasma glucocorticoid (GC) level in immobilized mice is suppressed by a 50-Hz electric field (EF) in an EF strength-dependent manner. The present study aimed to assess the anti-stress effect of EFs in three scenarios: exposure to an EF of either 50 or 60 Hz, which are the standard power frequencies in most regions; varying levels of environmental brightness during EF exposure; complete or partial shielding of the mouse from the EF. We compared the GC levels and blood parameters among control, EF-alone, immobilization-alone, and co-treatment groups. There was no difference between EFs of 50 and 60 Hz in terms of the suppression of the immobilization-induced increase in GC, that is, the anti-stress effect upon EF exposure. Examination of the effects of three environmental illuminance levels, 0, 200, and 490 lux, revealed that the effect of the EF was influenced by environmental illuminance. Shielding of the mice from the EF by wrapping the animals with an electrically conductive sheet inhibited the EF effect, which showed a negative correlation with the area shielded. Hence, environmental illuminance and the body area exposed to the EF might influence the effects of an EF on stress-induced increases in plasma GC levels in mice. Because stress plays an important role in the onset and progression of various diseases, these findings may have broad implications for understanding the efficacy of EFs in health. Bioelectromagnetics. 39:516-528, 2018 © 2018 Wiley Periodicals, Inc.