1997; Salford  et al ., 2003; Eberhardt  et al ., 2008).  They found that exposure of rats to 0.915GHz pulse-modulated signals (mainly 2 hour exposures) led to increases in  albumin  (fairly large blood plasma protein) entering the brain.  Interestingly they found that the  very low SARs  0.4-8mW/Kg had the greatest effect (Persson  et al ., 1997).