Suppression of Glucocorticoid Response in Stressed Mice Using 50 Hz Electric Field According to Immobilization Degree and Posture

SIMPLE SUMMARY: With an increasing demand for electricity and electrical equipment, humans are routinely and unintentionally exposed to electric fields (EFs); no significant adverse effects have been identified from exposure to EFs, but slight physiological effects are known to occur. There are, however, methods and devices that expose subjects to EFs for medical purposes. The effects of such methods are not strong and primarily involve the physical properties of EFs, which are invisible and easily disturbed, yet the mechanisms of the biological effects of such EFs have not been identified. We have developed a simple experimental system that allows us to reproducibly observe the inhibitory properties of EFs on the glucocorticoid response to added stress. Using this system, we have revealed the biological effects of EFs. This study has shown that human body posture may affect action of the EF and that it is important to adjust the degree of immobilization in order to capture the effect of the EF. The results of this study provide useful information not only for medical applications of EFs but also for the assessment of risks to health. ABSTRACT: Various studies on immobilized BALB/c mice to evaluate changes in hormone levels associated with stress responses have advanced the characterization of multiple aspects of the biological actions of extremely low-frequency (ELF) electric fields (EFs). In this study, we aimed to investigate the effect of mouse posture on its stress responses and evaluate the importance of adjusting the stress degree in the model. Mice were immobilized inside centrifuge tubes and exposed to an ELF EF generated between parallel plate electrodes. Blood was collected under anesthesia immediately after EF exposure, and plasma glucocorticoids were assayed. The inhibitory effects of EFs on glucocorticoid elevation by immobilization were reproduced regardless whether mice were in the abdominal or lateral recumbent position, for the EF vector delivered to mice through the sagittal or frontal plane. The effect of ELF EF was reproduced in moderately and mildly stressed mice but not in severely immobilized mice. Hence, adjusting the stress degree is critical to the reproducibility of the results for this model. We characterized the effects of ELF EF on homeostasis, including the stress response, and provided valuable information for the scientific evaluation of the biological risks and medical applications of ELF EF.