Cosquer and colleagues performed three experiments in this study. The overall aim was to test whether electromagnetic fields (EMFs) identical to the ones used by Lai et al. (1992) were able to alter levels of anxiety in male Sprague-Dawley rats.
In the first two experiments the anxiety responses were found to decrease with decreasing light intensity and to be attenuated by diazepam. The anxiety responses were tested by the plus-maze test, a standard test for animal anxiety. The maze is elevated 70 cm above the floor and is formed by four arms in the shape of a cross. Two arms are bordered by high walls (closed arms) and the other two have no borders (open arms). Rats placed at the centre of the maze have a strong preference for the closed arms.
The rats were habituated to lab conditions for 10 days prior to the experiments, and were handled for 4-5 minutes per day for the last 5 days of the habituation period. For the EMF experiment, the rats were brought to the testing room about 5 minutes before exposure started. The exposed group were placed in a waveguide for 45 minutes and radiated at 2.45 GHz (2µs pulse width, 500 pulses per second, whole-body and time-averaged SAR 0.6 W/kg ± 2dB, brain-averaged SAR of 0.9 W/kg ±3dB). Twelve rats were tested at low light intensity (2.5 lux), and 12 at 30 lux. Two groups of 12 rats were sham-exposed (placed in the waveguide but not radiated), one at low lux and the other at high lux before being tested in the maze. Similarly two groups of naive rats (not placed in the waveguide) were tested.
EMF exposure failed to induce any significant effect on anxiety responses in the plus maze.
In their discussion, the authors refer to the 1992 paper by Lai et al., in which they reported that a single exposure to EMF identical to that used by the authors induced an increase in the concentration of benzodiazepine responses in the cerebral cortex. This increase was not seen with repeated exposure. The situation is complicated by the fact that others have reported that stressful situations are associated with a decreased number of benzodiazepine receptors.
Cosquer and colleagues in another study had failed to replicate a report by Lai et al. (1994), in which EMF-induced changes were observed in a spatial working memory test (Cassel et al., 2004). Cosquer et al. speculate that the different results might be explained by differences in anxiety levels, perhaps due to the method of habituation to lab conditions and handling techniques.