Sprague Dawley rats (4-week and 10-week old) were exposed to 1.5 GHz (PDC) RF at 0, 2, or 6 W/kg (brain average with 6 W/kg corresponding to 0.4 W/kg whole body average) for 90 minutes per day, 5 days / week for 1 or 2 weeks and evaluated for BBB leakage (via permeability of injected FITC-dextran / fluorescent microscopy). Expression of brain endothelial cell markers (claudin-1,-5, aquaporin-4, P-glycoprotein, and acma-bolin) was also performed using rtPCR (as any disruption of BBB would also be thought to affect these gene products). Corresponding whole-body SAR levels were 0.87 W/kg 4-week old and 0.29 W/kg for 10-week old animals. The authors suggest that 4- and 10-week old rats roughly corresponded to similar developmental stages in children and teenagers, respectively. The authors reported no effect on blood brain barrier permeability or histopathological changes such as gliosis or degenerative lesions. There was an increase in the expression of aquaporin-4 transcript (abundant CNS water channel protein) in the 6 W/kg group, but no associated downstream protein increase and it did not correlate with any observed biological or histological endpoints suggesting the finding may have been an artifact.