From the Research Laboratories, Food and Drug Directorate, Department of National Health and Welfare, Ottawa, Canada
Although the effects of fluoride on dental caries, bone formation, enzyme activity and general health have been investigated extensively, little information is available regarding its effect on the activity of the central nervous system (CNS). Among the few studies in the literature relevant to the CNS are those on cholinesterase (ChE) inhibition (MATTHES; NACHMANSOHN 1939; DYBING & LOE 1956), and on depression of electrical activity of the cerebral cortex of the “encephale isole” cat (MORUZZI 1938). In rats, sodium fluoride was reported to potentiate the effect of certain centrally acting agents including pentobsarbitone and diphenylhydantoin, possibily inhibiting ChE (LU et al. 1961; RICE & LU 1963).
Several investigators (RUSSELL 1956; WATSON 1959; LASAGNA & LATIES 1959; RUFFIN 1963) have suggested that toxic effects of drugs on the CNS may show up earlier in altered behavioural patterns than in more readily observable physiological changes. Thus, subtle changes in behaviour, such as impaired memory or learning ability, might occur at lower dosage levels than, for instance, changes in respiration and heart rate, gross motor incoordination or general depression of activity. It was therefore considered desirable to investigate the effect of sodium fluoride on maze learning ability in rats, and to use petobarbitone sleeping time as a comparative physiological measure.
Methods: 45 male hooded rats were divided into three equal groups at the age of 42 days. Group 1 was given a standard laboratory diet*) to which had been added 150 ppm of NaF (68 ppm of F–), and Group 3, the control group, received the standard diet without any added fluoride. The concentrations of NaF added to the diets were the dsame as those reported by LU et al.
*) Ground Master Fox Cubes (fluorine content 0.002%), Maple Leaf Milling CO, Toronto, Ont.