Time‐dependent changes in the suppressive effect of electric field exposure on immobilization‐induced plasma glucocorticoid increase in mice

We recently reported that increased glucocorticoid (GC) levels in immobilized mice were suppressed by exposure to a 50‐Hz electric field (EF) in kV/m‐dependent and exposure duration‐dependent manners. Here, we characterized time‐dependent changes in the effect of EF exposure in immobilized mice. Using control, EF‐alone, immobilization‐alone, and co‐treated groups, plasma GC levels, and blood properties were first measured (0–60 min) to observe changes induced by each treatment and measured again (60–120 min) to assess recovery from each treatment. The 50‐Hz, 10‐kV/m EF was formed in a parallel plate electrode. Co‐treated mice were exposed to the EF for 60 min for the first measurement and were immobilized for the second half (30–60 min) of the EF exposure period. Plasma GC levels did not change significantly over time in the control and EF‐alone groups. GC levels in the immobilization‐alone and co‐treated groups increased after immobilization, peaking 30 min after the start of immobilization and then decreasing gradually; however, the GC peak was lower in the co‐treated group than in the immobilization‐alone group ( P  < 0.05 at 50 and P  < 0.001 at 60 min). Red blood cell counts, hemoglobin levels, and hematocrit values increased after immobilization but were not affected by the EF. Our findings indicate that the EF did not shift the peak of the time‐dependent increase in plasma GC levels in immobilized mice but simply reduced it. Bioelectromagnetics. 38:272–279, 2017. © 2017 Wiley Periodicals, Inc.