Histopathological Evaluation Of  Rat Brain Exposed to Different Fluoride Doses

Method: Female rats were randomized into three groups: Control group received tap water (fluoride concentration <0.05 ppm); experimental groups received 30 and 100 ppm fluoride in drinking water during mating, breeding and lactation periods. 63 pups born from all groups received the same water regimen and were followed up for 1, 3, and 5 months. Dental fluorosis was quantified using a fluorosis index based on the identification of incisor enamel defects according to their severity and quantity. Sections from cerebellum, cerebrum and hippocampus regions were evaluated under a light microscope. CAT and SOD immunoreactivity was determined by evaluating  entire sections on high power field (X400). Immunostaining for CAT and SOD was evaluated according to both staining intensity and frequency of cells. Data was analyzed by chi-squared test.

Result: Rats exposed to 30 ppm fluoride didn’t show any significant histopathological alterations, whereas rats exposed to 100 ppm fluoride showed neurodegenerative changes. The CAT immunoreactivity after 1 and 3 months  in cerebellum was high in 100 ppm fluoride group than 30 ppm fluoride and control groups and it was statistically significant (p<0.01).  CAT immunreactivity in all regions was high in 30 ppm fluoride group than 100 ppm fluoride and control groups after 5 months and the difference was statistically significant (p<0.01). SOD immunoreactivity was increased in all groups (p>0.05).

Conclusion: Within the limitations this study, we concluded that prolonged exposure to high fluoride in drinking water may cause  neurodegenerative changes in  the brain tissue of rat that may be associated with oxidative stress.