The study was divided into two parts. In the first part, it was tested if restraint induces stress in rats. 2 groups of rats (n=3 each) were restrained by wrapping each rat within a thin polyethylene sheet for 30 minutes. Group 1 was injected with 1 mg/kg of diazepam 30 minutes before the restraint period, group 2 received no injection.
In the second part, the effects of restraint in combination with exposure to the electric field was examined. Rats were divided into the following groups (n=6 each): 3) sham exposure (no restraint, no injection), 4) sham exposure and restraint, 5) exposure to the 50 Hz electric field and restraint, 6) sham exposure, restraint and diazepam injection (remark EMF-Portal: apparently, there was a further group using probably non-restrained rats exposed to the electric field, but it is not mentioned in the methods). Restraint was conducted for 30 minutes during the second half of the exposure period.
Stress was measured by means of different markers in the blood: an increase of ACTH is a marker for emotional stress and is accompanied by an increase of glucose, whereas an increase of lactate and pyruvate is a marker for physical stress from muscle activity.All rats were ovariectomized, to avoid influences of the estrous cycle on the results.
Exposure duration: continuous for 60 min
|Chamber||cylindrical plastic cage (400 mm diameter, 400 mm height); the cage had slits (length: 100 mm, width: 5 mm) around at intervals of 5 mm from each other|
|Setup||two electrodes made of stainless steel (1200 x 1200 mm) placed over and under the cylindrical cage; a stable alternating current (50 Hz, 7000 V) was applied to the upper electrode|
|Sham exposure||A sham exposure was conducted.|
|electric field strength||17.5 kV/m||-||-||-||-|
In part 1, the levels of ACTH were significantly increased in rats with (group 1) and without (group 2) diazepam after restraint compared to the pre-restraint value, although they were lower in group 1. Glucose and lactate levels were significantly increased in group 1 directly after restraint compared to pre-restraint values, but already 30 minutes later, there were no significant differences anymore.
In part 2, restraint rats (group 4) showed significantly increased ACTH levels compared to the sham exposure group (group 3). However, in combination with exposure to the electric field (group 5), this level was significantly lower than in group 4 and in combination with diazepam (group 6) it was in turn significantly lower than in group 5. Plasma lactate levels were significantly lower in groups 5 and 6 compared to group 4. (remark EMF-Portal: an exposure of probably non-restrained rats to the electric field had no effect on the ACTH level).
All other parameters did not show any significant differences between the groups. Exposure to the electric field did not cause pathological changes and the data of the hematologic parameters were not stated.
The authors conclude, that exposure of stressed rats to a 50 Hz electric field could suppress some stress markers in the blood via an unknown mechanism of action.