Schirmacher A, Winters S, Fischer S, Goeke J, et al. (2000)

This study used an in vitro model of the blood-brain barrier (BBB). This model, which consisted of rat brain cells growing in a culture with pig blood vessel cells, was tested using electron microscopy and immunocytochemistry, and found to reflect vital properties of the BBB. The cultures were exposed to 1800 MHz microwave radiation pulsed at a repetition rate of 217 Hz. The overall average SAR was 0.3 W/kg, with a maximum value of 0.46 W/kg at any point. No significant rise in temperature could be detected within the measurement resolution of about 0.1° C.
The BBB was tested using sucrose labeled with radioactive carbon. The permeability of both controls and exposed samples rose during the experiment, but that of the exposed samples was twice as high by four days. This result was highly significant statistically.

The authors conclude that their experiment showed "a definite and reproducible effect of microwave exposure on the physiological properties of the BBB in vitro".