In this publication, results from 32 individual experiments were evaluated in a pooled analysis. Data from Hori et al. 2015, Harakawa et al. 2017, Hori et al. 2017, Hori et al. 2018, Harakawa et al. 2020 and from unpublished experiments were used. For glucocorticoid level analysis, data from all 32 experiments were pooled. For the haematological analyses, data from 6 experiments (all unpublished) were pooled, and for the metabolome analysis, data from one unpublished experiment were used.
Most experiments used the following groups: 1) immobilization stress and exposure to the electric field, 2) exposure to the electric field only, 3) immobilization stress only, 4) control group.
Exposure duration: 60 minutes
|Exposure duration||60 minutes|
|Chamber||cylindrical plastic cage (diameter: 200 mm, height: 100 mm) with slits (length: 100 mm, width: 5 mm) throughout at intervals of 5 mm to prevent smudges (from faeces or saliva) from disturbing the formation of a stable electric field; stress was induced by the immobilisation of each mouse separately inside a 50 mL centrifuge tube|
|Setup||the exposure system consisted of two stainless steel electrodes (1,000 mm × 600 mm) that were placed above and under the cylindrical cage; current was applied to the upper electrode, whereas the lower electrode was grounded; separate cages and tubes were used for each animal; the temperature inside the cage was 25 °C ± 3 °C during exposure or sham exposure; the humidity was maintained between 45 and 55%; the electric field intensity had an error margin of ± 0.1% inside the cage; mice in the co-exposure group were immobilised during the second half (30 min) of the exposure period|
|Sham exposure||A sham exposure was conducted.|
|electric field strength||10 kV/m||-||measured||-||-|
The plasma glucocorticoid level was significantly reduced in immobilized mice exposed to the electric field (group 1) compared to immobilized mice without electric field exposure (group 3). In mice only exposed to the electric field (group 2) the glucocorticoid level was slightly but significantly increased compared to the control group. The immobilisation‑induced increase in lactate dehydrogenase, glutamic oxaloacetic transaminase, and glutamic pyruvic transaminase level (markers of tissue damage) was significantly suppressed in immobilized mice exposed to the electric field. In the metabolome analysis, the changes in corticosterone, leukotrienes, and hydroxyeicosatetraenoic acids (markers of inflammation) showed a pattern similar to that of the plasma glucocorticoid level.
The authors concluded that exposure to a 50 Hz electric field might reduce the stress and stress‑induced tissue damage and inflammation in immobilized mice. However, it might promote stress in the absence of immobilization-induced stress.