An Evaluation of Neurotoxicity Following Fluoride Exposure from Gestational Through Adult Ages in Long-Evans Hooded...

At elevated levels, fluoride (F^-) exposure has been associated with adverse human health effects. In rodents, F^- exposure has been reported to induce deficits in motor performance and learning and memory. In this study, we examined Long-Evans hooded male rats maintained on a standard diet (20.5 ppm F^-) or a low F^- diet (3.24 ppm F^-) with drinking water exposure to 0, 10, or 20 ppm F^- from gestational day 6 through adulthood. At postnatal day 25, brain F^- levels were 0.048 or 0.081 microg/g and femur 235 or 379.8 microg/g for 10 and 20 ppm F^-, respectively. Levels increase with age and in adults, levels for plasma were 0.036 or 0.025 microg/ml; for the brain 0.266 or 0.850 microg/g; and for the femur, 681.2 or 993.4 microg/g. At these exposure levels, we observed no exposure-related differences in motor, sensory, or learning and memory performance on running wheel, open-field activity, light/dark place preference, elevated plus maze, pre-pulse startle inhibition, passive avoidance, hot-plate latency, Morris water maze acquisition, probe test, reversal learning, and Y-maze. Serum triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH) levels were not altered as a function of 10 or 20 ppm F^- in the drinking water. No exposure-related pathology was observed in the heart, liver, kidney, testes, seminal vesicles, or epididymides. Mild inflammation in the prostate gland was observed at 20 ppm F^-. No evidence of neuronal death or glial activation was observed in the hippocampus at 20 ppm F^-.