The effect of a 900-MHZ electromagnetic field applied between postnatal days 21 and 49 on the morphology of the male rat hippocampus at different stages of development

The purpose of this study was to investigate potential changes in the morphology of the hippocampus at different stages of development of male rats exposed to 900-megahertz (MHz) electromagnetic field (EMF). Thirty-six Sprague Dawley rats at the age of 21 days were used. Rats were divided equally (n = 6) into Control 1, Control 2, Sham 1, Sham 2, EMF 1 and EMF 2 groups. Continuous 900-MHz EMF was applied to the rats in the EMF groups for 1 hour a day over 29 days, starting from postnatal day 21, within an EMF application cage. Sham group rats were placed inside the EMF cage for 1 hour a day over 29 days without EMF exposition. No procedure was performed tothe control group rats. The Control 1, Sham 1 and EMF 1 group rats were sacrificed at day 50, and Control 2, Sham 2 and EMF 2 group rats at day 79. No procedure was performed to the '2' group rats between days 50 and 79. The sacrificed rats' brains were removed, embedded in blocks following routine histological procedures and sectioned using a microtome. The sections were stained with cresyl fast violet, hematoxylin and eosin (H&E) and TUNEL. Pyramidal cell numbers at the cornu ammonis were counted using stereological methods in sections stained with cresyl fast violet. Histopathological evaluations were performed in the sections stained with H&E and cresyl fast violet, and apoptotic index evaluations were performed on TUNEL-stained sections. Vacuolization, pyramidal cells with dark cytoplasm and irregularities in cell array in the hippocampus and partial separations in the hilum were determined at histopathological analysis. Apoptotic index values of the EMF (0.05) groups were significantly higher than those of the other groups. Stereological analysis revealed a statistically significant decrease in the pyramidal cell numbers in the EMF groups compared to the other groups, but no difference between the two EMF groups exist. In conclusion, on the basis of our study findings, 900-MHz EMF applied on postnatal days 21-49 caused histopathological changes in the male rat hippocampus, and the effect of EMF persisted between days 50 and 79, when no additional exposure was taken place.