Twenty-four Wistar rats, weighing 100–120 g upon initiation of this study, were divided randomly into three groups each containing four male and four female animals. The diet of all of the animals contained low-fluoride (4 ppm fluoride) in order to avoid possible interference from the level of fluoride in the drinking water. Throughout the study, the animals were housed in stainless-steel cages suspended in stainless-steel racks; the humidity ranged from 30 to 55%; and the temperature remained between 22 and 25 ◦C. The control rats were given access to drinking water containing 0.6 ppm fluoride. The other two groups of rats received the same water to which was added 30 or 100 ppm fluoride (NaF). This diet and water were administered to ad libitum for 7 months, after which the animals were sacrificed and their brains dissected out and stored at −80 ◦C until further analysis.