Testylier G, Tondulu L, Malablau R, Debouzy JC (2002).
The authors used a microdialysis technique to study acetylcholine (ACh) release in the hippocampus of rats after exposure to radiation from two radiofrequency fields. The microdialysis uses a membrane implanted in the brain that allows the extraction of brain chemicals as they are released.
The first experiment involved exposure to 2450 MHz CW microwaves for 1 hour. A power density of 2 mW/cm² was used for 4 rats, with a whole body averaged SAR of 3.26 W/kg. Another 15 rats were exposed at a power density of 4 mW/cm², at a SAR of 6.52 W/kg. A control group of 14 rats was also studied. The rats exposed at 2 mW/cm² did not show a significant release of ACh. Those exposed at 4 mW/cm² had a significant 40% decrease in mean ACh release, maximal at 5 hours after exposure.
The second signal used was 800 MHz for 1 or 14 hours, and the averaged SAR was 0.325 W/kg. Those exposed for 1 hour showed no effect, but those exposed for 14 hours showed a 43% decrease during the hours of 11 p.m. to 4 a.m. The ACh levels returned to normal by the end of the exposure period.
The authors do not think that the observed effects at 2450 MHz were related to thermal effects although it should be noted that the SAR was high. They do not comment on possible temperature influences of the 800 MHz experiment.