Fluoride Action Network

Fluoride’s effect on the brain. Submission to the NRC on April 19, 2004


April 19, 2004

Submission to:
National Research Council Committee:
Toxicologic Risk of Fluoride in Drinking Water; BEST-K-02-05-A
c/o Susan Martel <smartel@nas.edu>

Ellen Connett
Fluoride Action Network Pesticides Project
82 Judson Street, Canton NY 13617
Email: pesticides@fluoridealert.org
Tel: 315-379-9200

Re: Fluoride’s effect on the brain.

For at least 2 decades reports have been published on NaF’s effect on brain. The overwhelming majority of these studies have not been considered in any US review of fluoride’s effects. In just the last 10 years numerous studies have been published and they have raised the level of concern about the impacts of increasing fluoride exposure on the brain, especially the effects on the most vulnerable in our society: the fetus, child, and the elderly.

Approximately 30% of US children are estimated to have dental fluorosis in the US. This large segment of young children show signs of overexposure to fluoride by visible damage to teeth. Dental fluorosis is known to occur at an age when a child’s brain is undergoing significant development. While we know that fluoride crosses the placenta, we know little of its impact on the human fetal brain. In this context an abstract of a 1992 study by Du (The effect of fluorine on the developing human brain) revealed adverse effects on the brain of aborted fetuses between the 5-8th month of gestation from an endemic fluorosis area compared with those from a non-endemic area. Because of these unique factors (overexposure to fluoride during significant brain development) we urge the committee to give serious consideration to fluoride’s impact on the brain.

Some brief comments on ATSDR’s most recent 2003 Toxicological profile for fluorides, hydrogen fluoride, and fluorine (released in March 2004).

ATSDR dismisses effects on brain in two ways:

1. By not citing the literature. We list 60 studies below. Of these, 52 are not cited by ATSDR. Of the 8 that are cited:

2. In the few cases ATSDR cites studies, it is dismissive- for example

ATSDR cites Whitford et al. (2003) to counter Mullenix et al. (1995) despite the fact that the Whitford et al. paper was “only available as an abstract (page 111),” and despite the fact that Mullenix’s study has gained support from at least 6 other rat studies – which ATSDR doesn’t discuss (Bhatnagar 2002; Ekambaram 2001; Paul 1998; Sun 2000; Zhang 1999, 2001). While these studies have employed different methods than Mullenix et al (1995), they are consistent in that they have also found that fluoride impacts behavior and/or learning.

As to the Varner et al. 1998 study, ATSDR states:

This study did not assess neurofunction; thus, it is difficult to assess the toxicological significance of these effects.

ATSDR’s lack of discussion of the findings of this important low-dose, long-term rat study is bewildering. ATSDR had over 5 years to give context to the findings in NaF-treated rats of

• beta amyloid plaques (the classic brain abnormality of Alzheimer’s disease)
• increased levels of aluminum in the brain (an important component of the neurological damage in Alzheimer’s).
• the finding that fluoride facilitates aluminum’s crossing of the blood brain barrier.
(ATSDR also didn’t mention the kidney disorders found in the NaF-treated group.)

The following studies demonstrate that ATSDR either has no familiarity with the literature on fluoride’s effects on brain or has allowed itself to be mired in a highly unscientific partisanship.

While most of these studies are in vivo, there are a number which probe mechanisms with in vitro studies with tissue slices etc. and a few others which use fluoride as a diagnostic tool in determining the influence of other substances on G-protein functions. While we recognize that not all these studies may be of use in determining a LOAEL, we have included them to facilitate a broader understanding of fluoride’s ability to distort the normal functioning of the brain.

Some studies reporting effects on the brain from sodium fluoride

Note: the following are a limited number of studies that have found adverse effects on the brain with NaF. Not included are numerous studies on G-Proteins and NaF due to lack of time to condense results. Also not included are the many studies on aluminum fluoride.

Date Effects Study



Fluoride concentration in rat hippocampus was significantly correlated with the dosage of fluoride, and there were significant differences among high dosage group [(13.03 +/- 1.79) micro g/g], low dosage group [(9.83 +/- 0.92) micro g/g] and control

Zhonghua Lao Dong Wei Sheng Zhi Ye Bing Za Zhi. 2003 Apr;21(2):102-4.

[Studies on fluoride concentration and cholinesterase activity in rat hippocampus]

Zhai JX, Guo ZY, Hu CL, Wang QN, Zhu QX.

School of Public Health, Anhui Medical University, Hefei 230032, China.

Article in Chinese. Suggest NRC translate



NaF 0, 5, 10, 20, and 50 mg
15 weeks

Neuropathological changes occurred with loss of the molecular layer and glial cell layer in the brain tissues of rabbits exposed to the three higher fluoride doses. The Purkinje neurones exhibited chromatolysis and acquired a “ballooned” appearance. Nissl substance showed various degrees of decrease and even complete loss. Fragmented particles were retained in the perinuclear zone. The perikaryon showed vacuolization, and spheroid bodies were present in the neoplasm. These cytoplasmic inclusions appeared as various sized ovoid bodies or elongated eosinophilic masses due to which the nucleus was shifted to the periphery.

Fluoride 36: 95-105.2003

Histopathological investigation of fluoride-induced neurotoxicity in rabbits.

Shashi A.



recombinant human prion protein

Chemical unfolding studies in urea show that at low concentrations (below approximately 50 mM), all salts tested (sodium sulfate, sodium fluoride, sodium acetate and sodium chloride) significantly reduce the thermodynamic stability of the protein.

The observed decrease in the thermodynamic stability of huPrP90-231 in the presence of sodium fluoride, sulfate, acetate and chloride is highly unusual since these salts are generally known to have a stabilizing effect on proteins.

The present study provides direct experimental evidence that, at relatively low concentrations, a variety of salts including sodium fluoride, sodium sulfate, sodium acetate, and sodium chloride decrease the thermodynamic stability of the recombinant human prion protein.

To the best of our knowledge, no other protein has been reported to be destabilized by kosmotropes such as fluoride, sulfate or acetate. Therefore, the present finding points to rather unique properties of the prion protein.

The present data indicate that electrostatic interactions play an unusually important role in the stability of the prion protein. The abnormal effect of salts is likely due to the ion-induced destabilization of salt bridges (Asp144-Arg148 and/or Asp147-Arg151) in the extremely hydrophilic helix 1.

J Biol Chem 2003. Apr 3

Atypical effect of salts on the thermodynamic stability of human prion proteinApetri AC, Surewicz WK.

Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106.

Free full text article


high-frequency synaptic stimulation in the rat hippocampal CA1-isolated slice preparations

intracellular loading of the GABA(A) receptor blocker fluoride abolished the oscillatory responses in the pyramidal cells. Neuroscience 2003. 119(1):265-75

Excitatory gaba input directly drives seizure-like rhythmic synchronization in mature hippocampal CA1 pyramidal cells.Fujiwara-Tsukamoto Y, Isomura Y, Nambu A, Takada M.

Dept. of System Neuroscience, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu, 183-8526, Tokyo, Japan

2003 In an attempt to elucidate the mechanism by which excessive fluoride damages the central nervous system, the effects of exposure of PC12 cells to different concentrations of fluoride for 48 h on nicotinic acetylcholine receptors (nAChRs) were characterized here. Significant reductions in the number of binding sites for both [3H]epibatidine and [125I]alpha-bungarotoxin, as well as a significant decrease in the B(max) value for the high-affinity of epibatidine binding site were observed in PC12 cells subjected to high levels of fluoride. On the protein level, the alpha 3 and alpha 7 subunits of nAChRs were also significantly decreased in the cells exposed to high concentrations of fluoride. In contrast, such exposure had no significant effect on the level of the beta 2 subunit. These findings suggest that selective decreases in the number of nAChRs may play an important role in the mechanism(s) by which fluoride causes dysfunction of the central nervous system.

Toxicology. 2003 Feb 1;183(1-3):235-42.

Selective decreases of nicotinic acetylcholine receptors in PC12 cells exposed to fluoride.

Chen J, Shan KR, Long YG, Wang YN, Nordberg A, Guan ZZ.

Department of Pathology, Guiyang Medical College, Guiyang 550004, Guizhou, PR China.


MOUSE (Female)

Ultrastructural studies revealed neurodegenrative characteristics like involution of cell membranes, swelling of mitochondria, clumping of chromatin material etc, can be observed in cell bodies of CA3, CA4 and dentate gyrus (Dg).

Fluoride intoxicated animals also performed poorly in motor co-ordination tests and maze tests

Indian J Exp Biol. 2002 May;40(5):546-54.

Neurotoxicity of fluoride: neurodegeneration in hippocampus of female mice.

Bhatnagar M, Rao P, Sushma J, Bhatnagar R.

Dept. of Zoology, M.L.S. University, Udaipur 313 001, India. mbhatnagar@yahoo.com




The DNA damage in pallium neurons in rats of the fluoride group was much more serious compared with those of the control group

TUNEL positive cells were found in pallium, hippocampus and cerebellar granule cells in rats of fluoride group, whereas those in the control group were rare

Zhonghua Yu Fang Yi Xue Za Zhi. 2002 Jul;36(4):222-4.

[Studies on DNA damage and apoptosis in rat brain induced by fluoride]

Chen J, Chen X, Yang K, Xia T, Xie H.

Dept. of Environmental Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.

Article in Chinese. Suggest NRC translate




results suggest that fluoride enhances oxidative stress in the brain, thereby disturbing the antioxidant defense of rats Increased oxidative stress could be one of the mediating factors in the pathogenesis of fluoride toxicity in the brain.

Fluoride 2002; 35(3):153-160.

Brain lipid peroxidation and antioxidant systems of young rats in chronic fluoride intoxication.

Shivarajashankara YM, Shivashankara AR, Bhat PG, Rao SH

Correspondence: YM Shivarajashankara, Dept. of Biochemistry, MR Medical College, Gulbarga-585105, Karnataka, India. shivrajsym@yahoo.com



100 ppm F

rats exposed to 100 ppm fluoride showed significant neurodegenerative changes in the hippocampus, amygdala, motor cortex, and cerebellum. Changes included decrease in size and number of neurons in all the regions, decrease in the number of Purkinje cells in the cerebellum, and signs of chromatolysis and gliosis in the motor cortex. Full report

Fluoride 2002; 35(1):12-21 

Histological changes in the brain of young fluoride-intoxicated rats

YM Shivarajashankara, AR Shivashankara, P Gopalakrishna Bhat, S Muddanna Rao, S Hanumanth RaoCorrespondence: YM Shivarajashankara, Dept. of Biochemistry, MR Medical College, Gulbarga-585105, Karnataka, India. shivrajsym@yahoo.com



30 or 100 ppm F in their drinking water for 7 months

There was a significant reduction in the number of [3H]epibatidine binding sites in the brain of rats exposed 100 ppm of fluoride…
the number of [125I]alpha-BTX binding sites was significantly decreased in the brains of rats exposed to both levels of fluoride. Western blotting revealed that the level of the nAChR alpha4 subunit protein in the brains of rats was significantly lowered by exposure to 100 ppm, but not 30 ppm fluoride; whereas the expression of the alpha7 subunit protein was significantly decreased by both levels of exposure.Since nAChRs play major roles in cognitive processes such as learning and memory, the decrease in the number of nAChRs caused by fluoride toxicity may be an important factor in the mechanism of brain dysfunction in the disorder.

Neurotoxicol Teratol 2002 Nov-Dec;24(6):751-7

Chronic fluoride toxicity decreases the number of nicotinic acetylcholine receptors in rat brain.

Long YG, Wang YN, Chen J, Jiang SF, Nordberg A, Guan ZZ.

Dept. of Pathology, Guiyang Medical College, 550004, Guizhou, Guiyang, PR China




The main results showed that the learning capability of mice drinking higher concentration of fluoride presented remarkable deterioration.

The results suggested that selenium might antagonize the neurotoxicity of fluoride on behavior and morphology.

Wei Sheng Yan Jiu 2001 May;30(3):144-6

[Effects of selenium on the damage of learning-memory ability of mice induced by fluoride]Zhang Z, Shen X, Xu X.

College of Life and Environmental Science, Zhejiang Normal University, Jinhua 321004, China.

Article in Chinese. Suggest NRC translate



NaF in drinking water (0.5 g/L) to pregnant and lactating mice, from the 15th day of pregnancy to the 14th day after delivery.


Compared to the control group, reductions in the cerebellar and cerebral protein concentrations by 27% and 17%, respectively.

Consistent histological changes were present in the cerebellum of the treated mice with the external granular layer being markedly reduced or absent, the Purkinje cell bodies being poorly differentiated and arranged in a single layer at the surface of the internal granular layer, and with more apoptotic Purkinje cells being present.


Full report

Fluoride 2001; 34(3 ):165-173

Effect of fluoride on thyroid function and cerebellar development in mice

Mahmoud Trabelsi, Fadhel Guermazi, Najiba Zeghal

Correspondence: Dr N Zeghal, Animal Physiology Laboratory, Dept. of Biology, Faculty des Sciences de Sfax-Route de la Soukra-Km 3.5, 3038 Sfax BP802, Tunisia.




12 one-month-old albino rats were administered 100-ppm fluoride (as NaF) in their drinking water for 4 months.

In the brain and liver, MDA and GSH levels increased, as did the activities of GSH-Px and glutathione S-transferase (GST). The level of ascorbic acid increased in the brain, but it decreased in the liver. These results suggest that fluoride enhances lipid peroxidation in the red blood cells, brain and liver of rats and causes increased or decreased enzyme activity associated with free radical metabolism.

Full report

Fluoride 2001; 34(2):108-113

Effect of fluoride intoxication on lipid peroxidation and antitoxidant systems in rats

YM Shivarajashankara, AR Shivashankara, P Gopalakrishna Bhat, S Hanumanth Rao

2001 General serine-threonine phosphatase inhibitors such sodium fluoride, or ss-glycerophosphate and sodium pyrophosphate, or specific PP1 and PP2A inhibitors including microcystin-LR, protein phosphatase 2A inhibitor I(1) or protein phosphatase inhibitor 2 all abrogate H-Ras and K-Ras dependent Raf-1 activation in vitro.

Oncogene. 2001 Jul 5;20(30):3949-58.

Protein phosphatases 1 and 2A promote Raf-1 activation by regulating 14-3-3 interactions.

Jaumot M, Hancock JF.

Laboratory of Experimental Oncology, Department of Pathology, University of Queensland Medical School, Herston Road, Queensland 4006, Australia.




The results showed that the degree of DNA damage in the fluoride group and the selenium group were significantly greater than that in control group(P < 0.01). The damage in the fluoride group was even more serious.

It suggested that fluoride and selenium could induce DNA damage in pallium neural cells of rats respectively. Moreover, the joint antagonistic effect of selenium and zinc against fluoride was more obvious.

Definition of Pallium: – the central cortex with the subajacent white substance.


Wei Sheng Yan Jiu 2000 Jul;29(4):216-7

[Effects of selenium and zinc on the DNA damage caused by fluoride in pallium neural cells of rats]

Chen J, Chen X, Yang K.

Dept. of Environmental Health, Tongji Medical University, Wuhan 430030, China.

Article in Chinese. Suggest NRC translate





Results: Learning and memory abilities of high-fluoride exposed groups were significantly lower than that of the control group, while the brain ChE activities of high-fluoride exposed groups were significantly higher.
Conclusions: High fluoride concentration in drinking water can decrease the cerebral functions of mice. Fluoride is a neurotoxicant. 

Chinese Journal of Endemiology 2000;19(4):262-3

As cited and abstracted in Fluoride 2001; 34(1):80

Effects of high fluoride drinking water on the cerebral functions of mice

Sun Z-R, Liu F-Z, Wu L-N, et al.

Correspondence: Dept. of Environmental Health, Tianjin Medical University, Tianjin 300070, China.




Conclusions: There is a tendency for neurone apoptosis in chronic fluorosis in rats. It is most evident with changes in pathology. It is not likely that only one form of neurone damage exist in the process of chronic fluorosis. There are recessive changes and apoptosis in the process at the same time.


Chinese Journal of Endemiology 2000;19(2):96-8

As cited and abstracted in Fluoride 2001; 34(1):82

Study of the mechanism of neurone apoptosis in rats from the chronic fluorosis

Lu X-H, Li G-S, Sun B

Correspondence: Institute of Endemi c Diseases in Nornman Bethune University of Medical Sciences, Changchun 130021, China




NaF (20mg/kg/body weight) for 14 days


fluoride levels were significantly increased (p<0.01) in both brain and gastrocnemius muscle.

This study therefore shows that both brain and muscle are affected by fluoride with inhibition of some enzymes associated with free-radical metabolism, energy production and transfer, membrane transport, and synaptic transmission, but with an enhanced activity of XOD.

Fluoride 2000. Vol. 33 No. 1:17-26.

Effects of fluoride accumulation on some enzymes of brain and gastrocnemius muscle of mice

M Lakshmi Vani and K Pratap Reddy





CONCLUSION: Over uptake of fluoride for a long term could cause potential increase in the level of oxidative stress in the brain tissue.


Zhonghua Yu Fang Yi Xue Za Zhi 2000 Nov;34(6):330-2

[Influence of free radical inducer on the level of oxidative stress in brain of rats with fluorosis]

Shao Q, Wang Y, Guan Z.

Dept. of Neurology, Guiyang Medical College, Guizhou 550004, China.

Article in Chinese. Suggest NRC translate



F in drinking water


the learning ability of mice drinking high concentration of fluoride presented remarkable deterioration, the thickness of post-synaptic density (PSD) was decreased, and the width of synaptic cleft was remarkably increased. The results suggested that the impairment on the learning capability induced by fluorosis may be closely related with the pathological changes of synaptic structure in the brain of mice. Wei Sheng Yan Jiu. 1999 Jul;28(4):210-2.

[Effect of fluoride exposure on synaptic structure of brain areas related to learning-memory in mice]Zhang Z, Xu X, Shen X, Xu X.

Article in Chinese. Suggest NRC translate


in vitro system of cultured hippocampal neurons from foetal rats

It was concluded that aluminium interferes with the metabolism of the neuronal cytoskeleton and that this interference is potentiated by fluoride.

Arch Physiol Biochem. 1999 Feb;107(1):15-21.

Fluoride enhances the effect of aluminium chloride on interconnections between aggregates of hippocampal neurons.

van der Voet GB, Schijns O, de Wolff FA.

Toxicology Laboratory Leiden University Medical Center Leiden, The Netherlands.




Fluoride, which is used commonly as a pharmacological tool to activate phosphoinositide-phospholipase C coupled to the heterotrymeric Gq/11 proteins, inhibited the phosphorylation of phosphatidylinositol (PtdIns) to polyphosphoinositides (PtdIns4P and PtdIns4,5P2) in membranes from rat brain cortex.

our data show that fluoride, at a concentration similar to that used to stimulate directly Gq/11-coupled phospholipase C, effectively blocks the synthesis of phospholipase C substrates from PtdIns.

Int J Dev Neurosci 1999 Jul;17(4):357-67

Fluoride-induced depletion of polyphosphoinositides in rat brain cortical slices: a rationale for the inhibitory effects on phospholipase C.Sarri E, Claro E.

Departament de Bioquimica i de Biologia Molecular, Facultat de Medicina, Universitat Autonoma de Barcelona, Spain.



Intracellular blockade of GABA receptors with fluoride reveals a novel component of evoked GDPs


J Neurophysiol 81: 2095-2102, 1999

Glutamate Controls the Induction of GABA-Mediated Giant Depolarizing Potentials Through AMPA Receptors in Neonatal Rat Hippocampal Slices

Sonia Bolea (1), Elena Avignone (2), Nicola Berretta (2), Juan V. Sanchez-Andres (1), Enrico Cherubini (2)

1. Departamento de Fisiologia, Instituto de Bioingenieria, Universidad Miguel Hernandez, Campus de San Juan, 03550 San Juan, Alicante, Spain;
2. Neuroscience Program and Istituto Nazionale Fisica della Materia Unit, International School for Advanced Studies, 34014 Trieste, Italy



30 or 100 ppm F for 3, 5, and 7 months.


The results demonstrate that the contents of phospholipid and ubiquinone are modified in brains affected by chronic fluorosis and these changes of membrane lipids could be involved in the pathogenesis of this disease.


Neurotoxicol Teratol 1998 Sep-Oct;20(5):537-42

Influence of chronic fluorosis on membrane lipids in rat brain.Guan ZZ, Wang YN, Xiao KQ, Dai DY, Chen YH, Liu JL, Sindelar P, Dallner G.

Dept. of Pathology, Guiyang Medical College, Guizhou, China. jialiul@public.gy.gz.cn



pregnant rats ingested ad libitum fluorinated drinking water (5, 15, 50 ppm F-) during gestation and lactation


It was shown that the AChE activities of the SPM and peripheral RBCs in maternal rats exposed 5-50 ppm F- for 60 days were elevated significantly by 30.0-67.6% and 12.5-31.9% in a dose-dependent manner, respectively. The AChE activities of their offspring 80 days after birth were also increased (8.7-28.7% for SPM and 20.6-32.4% for RBC).


Biomed Environ Sci 1998 Mar;11(1):1-6

Actions of sodium fluoride on acetylcholinesterase activities in rats.Zhao XL, Wu JH.

Dept. of Environmental Toxicology, Chinese Academy of Preventive Medicine, Beijing, China.



1 ppm F in doubly distilled, deionized
drinking water


• a greater uptake of aluminum into the brain

• beta amyloid plaques

• Authors specultate that fluoride facilitates aluminum to cross the blood brain barrier


Brain Res 1998 Feb 16;784(1-2):284-98

Chronic administration of aluminum-fluoride or sodium-fluoride to rats in drinking water: alterations in neuronal and cerebrovascular integrity.

Varner JA, Jensen KF, Horvath W, Isaacson RL.

Psychology Department, Binghamton University, Binghamton, NY, USA.



We herein demonstrate that sodium fluoride (NaF) acts as a stress response inducer on HeLa and 9L rat brain tumor cells.


Induction of stress response and differential expression of 70 kDa stress proteins by sodium fluoride in HeLa and rat brain tumor 9L cells.


Dep. Life Sci., Natl. Tsing Hua Univ., Hsinchu 30043, Taiwan.


RAT (adult female)

NaF 20 or 40 mg:kg dose
level daily for 60 days

Spontaneous motor activity and motor coordination were tested in adult female rats after treating with sodium fluoride… A suppression of spontaneous motor activity suggests that fluoride has, by a central action, inhibited motivation of these animals to exhibit locomotor behavior. A cholinergic mechanism through a change in the activity of acetylcholinesterase may not account for this effect, since sodium fluoride treatment did not alter the activity this enzyme in brain regions. However, an involvement of monoamines may be proposed in view of previously reported finding that excessive fluoride intake has decreased the concentrations of 5-hydroxyindoleacetic acid and increased that of norepinephrine in rat brain.

Environmental Toxicology and Pharmacology 1998; 6: 187-191.

Effects of sodium fluoride on locomotor behavior and a few biochemical
parameters in rats

Vanaja Paul, P. Ekambaram, A.R. Jayakumar

Department of Pharmacology and Environmental Toxicology, Dr A.L.M.
Postgraduate Institute of Basic Medical Sciences, University of Madras, Taramani Chennai 600 113, India



66.3 mg/L and 221 mg/L F-containing water for 3, 5, and 7months


Coenzyme Q content of brain tissue in rats fed with fluorine-containing water decreased at early stage of fluorosis, but increased significantly at late stage. It is speculated that changes in content of coenzyme Q could correlate with changes in free radical levels induced by fluorine.


Zhonghua Yu Fang Yi Xue Za Zhi 1997 Nov;31(6):330-3

[Changes of coenzyme Q content in brain tissues of rats with fluorosis]

Wang Y, Guan Z, Xiao K.

Dept. of Scientific Research, Guiyang Medical College.

Article in Chinese. Suggest NRC translate



Wistar rats were fed with NaF until chronic fluorosis was induced

CONCLUSION: The metabolism of brain phospholipid might be interfered by fluoride accumulated in brain tissue, which is related with the degeneration of neuron. The changes of brain phospholipid could be involved in the pathogenesis of chronic fluorosis. Zhonghua Yi Xue Za Zhi 1997 Aug;77(8):592-6

[Influence of experimental fluorosis on phospholipid content and fatty acid composition in rat brain]Guan Z, Wang Y, Xiao K.

Guiyang Medical College.

Article in Chinese. Suggest NRC translate



Female MICE

Fluoride (50 ppm F as NaF) in dd water

Sixty-four CD-1 female mice were assigned to one of four water treatment groups: Control (distilled, deionized water) (C); Fluoride (50 ppm F as NaF) (F); Aluminum (100 ppm Al as AlCl3) (Al); and Al & F (50 ppm F & 100 ppm Al) (AlF). One-half of the animals in each group were mated. The study was terminated on the 5th days after parturition.

brain Al increased 168% in the F group, and 260% to 350% in the remaining three groups.

FASEB J 1997 Feb;11(3):A406

Effects of fluoride and aluminum exposure to dams prior to and during gestation on mineral compositions of bone and selected soft tissues of female mice dams and pups.

Koh ET, Clarke SLUniv. of Oklahoma Health Sci. Center, Oklahoma City, OK.



2.1 ppm in drinking water for 45 weeks

elevated brain level of aluminum

Neuronal abnormalities were observed in the NaF treated animals- especially in the deeper cell layers.

Both the AlF- and NaF-treated animals had substantial numbers of argentophilic cells on Bielchowsky staining and these cells showed condensed Nissl substance with hematoxylin and eosin staining. The NaF treatment also produced distortions of cells and, in some rats, cell losses could be demonstrated in particular brain regions. Both AlF3 and NaF induced vascular inclusions, although of a different character: the AlF3 produced the Al-based particles and the NaF produced the IgM inclusions.

Annals of the New York Academy of Sciences 825 152-166 1997

Toxin-induced blood vessel inclusions caused by the chronic administration of aluminum and sodium fluoride and their implications for dementia.

Isaacson RL, Varner JA, Jensen KF.

Department of Psychology, Binghamton University, New York 13902-6000, USA. isaacson@binghamton.edu


Small doses of sodium fluoride accelerated axonal transport (AT), and this correlated with a rise in cAMP levels in ventral roots. High doses of sodium fluoride decelerated AT more markedly in old rats.

Changes in AT could be an important mechanism of disordering the growth of neurons and innervated cells in old age.

Exp Gerontol 1997 Jul-Oct;32(4-5):441-50

Age-related changes in axonal transport.Frolkis VV, Tanin SA, Gorban YN.

Institute of Gerontology, Academy of Medical Sciences of Ukraine, Ukraine.



The activity and regulatory properties of the adenylate cyclase system of the rat striatum were studied. Agents such as Gpp(NH)p, forskolin, and NaF were found to show classical in vitro stimulation of adenylate cyclase activity in the striatum membrane fraction.

Neurosci Behav Physiol. 1998 Jul-Aug;28(4):392-6.

Adenylate cyclase system of the rat striatum: regulatory properties and the effects of gangliosides.

Plesneva SA, Nalivaeva NN, Zhuravin IA.

I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia.


Oxidative stress appears to contribute to neuronal dysfunction in a number of neurodegenerative conditions, notably including Alzheimer’s disease, in which cholinergic receptor-linked signal transduction activity is severely impaired.

activation with NaF of G-proteins coupled to phospholipase C was concentration dependently inhibited by H2O2, indicating impaired G-protein function. These effects of H2O2 are similar to signaling impairments reported in Alzheimer’s disease brain, which involve deficits in receptor- and G-protein-stimulated phosphoinositide hydrolysis, but not phospholipase C activity.

J Neurosci 1996 Oct 1;16(19):5914-22

Cholinergic stimulation of AP-1 and NF kappa B transcription factors is differentially sensitive to oxidative stress in SH-SY5Y neuroblastoma: relationship to phosphoinositide hydrolysis.Li X, Song L, Jope RS.

Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham 35294-0017, USA.



Behavior was tested in a computer pattern recognition system


Prenatal weanling and adult exposures all caused sex- and dose-specific behavioral deficits with a common pattern.

Males were most sensitive to prenatal day 17-19 exposure, while females were more sensitive to weanling and adult exposures. After weanling and adult exposures the severity of deficits increased with increasing F levels found in plasma and specific brain regions such as the hippocampus.

Neurotoxicol Teratol. 1995 Mar-Apr;17(2):169-77.

Neurotoxicity of sodium fluoride in rats

Mullenix PJ, Denbesten PK, Schunior A, Kernan WJ.




Calcium currents in CA1 neurons from rat hippocampus were studied with the whole-cell, patch-clamp technique. Under control conditions high-voltage-activated (HVA) calcium currents activated from membrane potentials of -80 mV and -40 mV underwent “run-down”. The rate of run-down of the current activated from -40 mV was significantly attenuated by inclusion of the G-protein activator NaF (1 mM) in the pipette and also irreversibly attenuated by brief batch application of NaF (10 mM)… It is suggested that activation of guanine nucleotide-binding proteins by NaF leads to a long-lasting attenuation of HVA calcium current run-down in hippocampal CA1 cells.

Exp Brain Res. 1995;106(3):505-8.

Attenuation of high-voltage-activated Ca2+ current run-down in rat hippocampal CA1 pyramidal cells by NaF.

Breakwell NA, Behnisch T, Publicover SJ, Reymann KG.

Department of Physiology, Trinity College Dublin, Ireland.



5, 10, 20, and 50 mg/kg body wt/day by subcutaneous injection for 100 days

In fluoride treated rabbits the brain showed significant decline (P <0.001) in soluble, basic total protein and free amino acid levels. RNA content rapidly decreased (P <0.001) in the brains of experimental animals compared to the controls. However, in male animals treated with 5 and 10 mg fluoride no statistically significant differences in RNA content of brain were observed. The depletion of proteins produced degenerative changes in purkinje cells of the cerebellar cortex.

Fluoride 1994; 27(3):155-159

Effect of long-term administration of fluoride on levels of protein, free amino acids and RNA in rabbit brain

Shashi A, Singh JP, Thapar SP

Department of Zoology, Punjabi University, Patiala 14702, India




Effects of NaF on Ca2+Mg(2+)-ATPase activity of synaptic membrane in rat brain were studied with in vitro or in vivo methods. Concentrations of NaF of 0.3, 1.6, 8.0, 20.0 and 40.0 mmol/L can significantly inhibit the activity of the enzyme with proportions of 6.6%, 18.0%, 41.0%, 55.5% and 63.1%, respectively, and with a half inhibitory concentration of 14.8 mmol/L reflecting an obvious dose-effect and time effect relationship. Analysis of enzyme substrate kinetics showed the effect that NaFhad was a non competitive inhibition. Activity of Ca2+Mg(2+)-ATPase on synaptic membrane in female rat brain showed a decreasing tendency after feeding with water fluorinated with 5, 15 and 50 mg/L of fluoride during their gestation and lactation for 50 days, and that in their newborn offsprings with 5 and 50 mg/L of fluoride was inhibited by 11.3 and 32.1%, respectively. Zhonghua Yu Fang Yi Xue Za Zhi 1994 Sep;28(5):264-6

[Effects of sodium fluoride on the activity of Ca2+Mg(2+)-ATPase in synaptic membrane in rat brain]Zhao XL, Gao WH, Zhao ZL.

Department of Environment Health Ningxia Medical College, Yinchuan.

Article in Chinese. Suggest NRC translate


(3) Excessive fluoride intake decreased 5-hydroxy indole acetic acid and increased norepinephrine in rat brain


Hua Hsi I Ko Ta Hsueh Hsueh Pao. 25(2):188-91.1994

[Effect of excessive fluoride intake on mental work capacity of children and a preliminary study of its mechanism]

Li Y, et al. 1994

Article in Chinese. Suggest NRC translate



15 aborted fetuses at 5-8th gestation month from an endemic fluorosis area compared with those from a non-endemic area

Stereological study of the brains showed that the numerical density of volume of the neurons and the undifferentiated neuroblasts as well as the nucleus-cytoplasm ratio of the neurons were increased. The mean volume of the neurons was reduced. The numerical density of volume, the volume density and the surface density of the mitochondria were significantly reduced. The results showed that chronic fluorosis in the course of intrauterine fetal life may produce certain harmful effects on the developing brain of the fetus.

Zhonghua Bing Li Xue Za Zhi 1992 Aug;21(4):218-20

[The effect of fluorine on the developing human brain]

Du L.

Department of Pathology, Guiyang Medical College.

Article in Chinese. Suggest NRC translate



NaF at 5, 10, 20 and 50 mg/kg BW/day was injected subcutaneously for 100 days

Biochemical studies showed hyperlipidemia, hyperphospholipidemia, and hypertriglyceridemia in the brain of treated animals of both sexes.

Fluoride exerts an inhibitory effect on the free fatty acids in brain of both sexes. The relevance of these results in experimental fluorosis is discussed.

Fluoride 1992; 25(2):77-84

Studies on alterations in brain lipid metabolism following experimental fluorosis

A Shashi

Department of Zoology, Punjabi University, Patala 147002, India



streptozotocin induced diabetic rats after 5 weeks of induction of diabetes

The net NaF stimulated AC activity in diabetic rats (109.5 +/- 11.4) was significantly lower than the control rats (154.3 +/- 16.3) (P less than 0.05).

It is concluded that diabetes mellitus in rats is associated with reduced post receptor activation of adenylate cyclase in cerebral microvessels

Res 1992 Jun 26;583(1-2):155-60

Beta-adrenergic receptor activity of cerebral microvessels in experimental diabetes mellitus.

Mooradian AD, Scarpace PJ.

St. Louis DVA Medical Center, MO.


Rat hippocampal slices were exposed briefly (12-15 min) to AlF4- (10 mmol/l NaF, 10 mumol/l AlCl3).

The effect on synaptic transmission in area CAl was measured using extracellular electrodes placed in the stratum pyramidale and stratum radiatum. During fluoride exposure, both spike and EPSP amplitude fell to very low levels.

It is concluded that NaF/ACl3 exposure induces an LTP-like process by G-protein activation,

Exp Brain Res 1991;84(3):680-4

Brief exposure to the G-protein activator NaF/AlCl3 induces prolonged enhancement of synaptic transmission in area CAl of rat hippocampal slices.Publicover SJ.

School of Biological Sciences, University of Birmingham, Edgbaston, UK.


RAT (Lactating)

2) During chronic fluorosis serum PRL level was decreased, however, PRL content in pituitary was increased. Electronmicroscopic examination showed accumulation of large
mature secretory granules and appearance of extremely large abnormal secretory granules in lactotroph cytoplasma. These finding indicate that
hormone release of pituitary lactotrophs is obstructed in lactating rats with fluorosis, and the toxic effect of fluoride is mediated by an enhanced function of dopaminergic system in hypothalamus.

ACTA PHYSIOL SIN; 43 (5). 1991. 512-517.

An experimental study of inhibition on lactation in fluorosis rats.


Neuroendocrine Res. Lab., China Med. Univ., Shenyang 110001.



160 cases of acute sodium silicofluoride poisoning due to accidental intake are reported in this paper… The cardiovascular findings were notable. Ninety-six cases had abnormal electrocardiographic findings. Abnormal heart rhythm and S-T segment changes were the main findings. These changes were positively correlated with the toxin amount of fluoride. Two cases died from sudden arrest of heart beat. Lung, kidney, liver, and brain functions were also impaired.

CHIN J PREV MED; 25 (5). 1991. 269-271.

The clinical features of 160 cases of acute sodium silico fluoride poisoning.

Dong Y et al.

First People’s Hosp., Wenling County, Zhejiang 317500

1990 It is concluded that fluoride ions inhibit agonist-stimulated inositol phospholipid breakdown via actions not only on G-proteins but also on phosphoinositide-specific phospholipase C substrate availability. Brain Res 1990 Dec 24;537(1-2):93-101

Multiple actions of fluoride ions upon the phosphoinositide cycle in the rat brain.Tiger G, Bjorklund PE, Brannstrom G, Fowler CJ.

Dept. of Pharmacology, University of Umea, Sweden.

1990 Evidence is presented to suggest that NaF affects the dephosphorylation of the formed [3H]inositol polyphosphates.

Eur J Pharmacol 1990 Jan 23;188(1):51-62

Effect of monovalent ions upon G proteins coupling muscarinic receptors to phosphoinositide hydrolysis in the rat cerebral cortex.

Tiger G, Bjorklund PE, Cowburn RF, Garlind A, O’Neill C, Wiehager B, Fowler CJ.

Dept. of Pharmacology, University of Umea, Sweden.


membranes from rat brain cortex


under conditions where breakdown of polyphosphoinositides by phospholipase C was dependent on PtdIns kinase activity, fluoride inhibited activation by GTP[S] plus carbachol of phospholipase C. When conditions allowed direct breakdown of PtdIns and precluded PtdIns kinase activity, the stimulatory effects of fluoride and GTP[S] plus carbachol on phospholipase C activity were additive. Biochem J 1990 Jun 15;268(3):733-7

Dual effect of fluoride on phosphoinositide metabolism in rat brain cortex.
Stimulation of phospholipase C and inhibition of polyphosphoinositide synthesis.Claro E, Wallace MA, Fain JN.

Department of Biochemistry, University of Tennessee, Memphis 38163.


NaF and guanosine 5′-O-thiotriphosphate [GTP(S)] stimulated the accumulation of [3H]inositol monophosphate ([3H]InsP) in rat brain cortical membranes, with half-maximal stimulation at 2 mM and 1 microM, respectively.

Our findings of different characteristics of GTP(S) and fluoride activation of polyphosphoinositide (PPI) hydrolysis suggest that separate regulatory mechanisms are involved in these two modes of stimulation in brain membranes. Activation of PPI hydrolysis by fluoride may be mediated by a direct stimulation of PPI phosphodiesterase or by activating a putative guanine nucleotide regulatory protein at a location distinct from the GTP-binding site.

J Neurochem 1990 Apr;54(4):1426-32

Guanosine 5′-O-thiotriphosphate and sodium fluoride activate polyphosphoinositide hydrolysis in rat cortical membranes by distinct mechanisms.Li PP, Sibony D, Warsh JJ.

Section of Biochemical Psychiatry, Clarke Institute of Psychiatry, Toronto, Ontario, Canada.


In this study we have used fluoride as a tool to investigate the involvement of G protein-coupled effector systems in the regulation of the depolarization-induced release of gamma-aminobutyric acid (GABA) from rat cerebral cortex.

From these studies, it is concluded that GABA release in cerebral cortex is subject to regulation by G protein-linked effector systems that are distinct from those affecting the release of [3H]ACh in cerebral cortex.

Neurochem 1990 Apr;54(4):1130-5

Modulation of gamma-aminobutyric acid release in cerebral cortex by fluoride, phorbol ester, and phosphodiesterase inhibitors: differential sensitivity of acetylcholine release to fluoride and K+ channel blockers.Gardiner IM, de Belleroche J.

Dept. of Biochemistry, Charing Cross and Westminster Medical School, London, England.



33-42-day old rat pups generated by three groups of female Wistar rats, which were given distilled water containing 0, 30 and 60 ppm NaF respectively beforehand as drinking water for 85 days

The results of behavior test showed that the latent period of pain reaction and that of conditioned reflex in the 30 ppm F and 60 ppm F groups were longer than that in the control group (P less than 0.05 or P less than 0.01). morphological examination of the pup brains showed that the nerve cell density of the 60 ppm F group was higher than that of the control group (P less than 0.05). Electronmicroscopically, mild degeneration of organelles of the nerve cells was observed in those brains of the 60 ppm F group. Zhonghua Bing Li Xue Za Zhi 1989 Dec;18(4):290-2

[Experimental study of behavior and cerebral morphology of rat pups generated by fluorotic female rat]Liu WX.

Article in Chinese. Suggest NRC translate



The mechanism of sodium fluoride (NaF) induced hypothermia was investigated on relations between the monoamine synthesis and metabolism in the rabbit brain.

Administration of NaF made a significant decrease in norepinephrine levels in the rabbit hypothalamus, but had no effect on 5-HT levels.

Shikwa Gakuho 1989 Mar;89(3):607-26

[The rabbit thermo-regulatory system. Effects of high dose of sodium fluoride]Machida H.

Article in Japanese. Suggest NRC translate



Since fluoride ions are known to activate G-proteins in the concentrations used in this study, these results may indicate the existence of a novel G-protein linked to receptor inhibition of phospholipase C. Biochem Biophys Res Commun 1988: Sep 15;155(2):664-9

Fluoride inhibits agonist-induced formation of inositol phosphates in rat cortex.Godfrey PP, Watson SP.

Dept. of Clinical Pharmacology, Radcliffe Infirmary, Oxford, United Kingdom.



results indicate that, in cerebral-cortical membranes, activation of phospholipase C by guanine nucleotides or fluoride directly increases a phospholipase C activity which specifically hydrolyses PIP2. Biochem J 1987 May 15;244(1):35-40

Guanine nucleotide and NaF stimulation of phospholipase C activity in rat cerebral-cortical membranes. Studies on substrate specificity.Litosch I.

Department of Pharmacology, University of Miami School of Medicine, FL 33101.



The blood-brain barrier fails to exclude the fluoride ion from nerve tissue.

Fluoride levels in brain reach a maximum approximately two hours after it has been administered.

Fluoride 1986; V 19, No 3: 108-112

Kenetics of fluoride penetration in liver and brain

Geeraerts F, Gijs G, Finne E, Crokaert R

Department of Biochemistry and Pharmacology, Vrije Universiteit, Laarbeeklaan, Brussels, Belgium.



No Abstract available

Zhonghua Bing Li Xue Za Zhi 1986 Dec;15(4):297-9

[Morphology of the brain of the offspring of rats with chronic fluorosis]

Guan ZZ.

Article in Chinese. Suggest NRC translate


We have attempted to suppress voltage-dependent conductances in hippocampal neurons by introducing various intracellular agents. Voltage-clamp studies were carried out using acutely dissociated hippocampal neurons from adult guinea pigs. Synaptic events were examined using intracellular recordings in the slice preparation… We also found that the anion fluoride could affect calcium conductance by an intracellular action. When anions other than fluoride were used for intracellular recordings, the voltage-dependent calcium current inactivated slowly and showed persistent activation at membrane potentials between -40 and -10 mV. In contrast, when fluoride was present intracellularly, the inactivation kinetics of the calcium current were accelerated and the persistent component of the current was largely suppressed. Intracellular recordings in the hippocampal slice showed that when electrodes contained cesium, QX 314, and fluoride, the spiking and nonlinear responses of the neuronal membrane to depolarization were blocked.


J Neurosci. 1986 Oct;6(10):2915-20.

Intracellular fluoride alters the kinetic properties of calcium currents
facilitating the investigation of synaptic events in hippocampal neurons.

Kay AR, Miles R, Wong RK.




The influence was studied in vitro of certain agents (adenosine, ADP, ATP, theophylline, together with F- ions) on the cAMP concentrations in the nuclear (N) and mitochondrial (M) fractions from different areas of rat brain. F- ions caused a slight decrease of the cAMP concentrations in nuclear fractions of the thalamus with hypothalamus and a marked decrease of this cyclic nucleotide in M fractions from the cerebral cortex.


Acta Physiol Pol 1984 May-Jun;35(3):199-206

Effect of certain agents on subcellular cAMP level in different areas of rat brain.Janiszewska G, Lachowicz L, Wojtkowiak R.




Accidental ingestion of NaF tablets

.. a 3-year-old boy who swallowed 200 sodium fluoride tablets (1 mg fluoride each) for a dose of 16 mg fluoride/kg body weight (Eichler et al. 1982).
… The boy died 7 hours after fluoride ingestion. Upon autopsy, hemorrhagic edema of the lungs, hemorrhagic gastritis, and massive cerebral edema were observed.As cited by ATSDR (2003), page 74

Int J Clin Pharmacol Ther Toxicol. 1982 Jul;20(7):334-8.

Accidental ingestion of NaF tablets by children–report of a poison control center and one case.

Eichler HG, Lenz K, Fuhrmann M, Hruby K.



The effects of fluoride (F-) administration were studied on 2 groups of weanling male Wistar rats, a control fed a basal diet containing 0.09 mg% F- and the other fed a diet containing 50 mg% F- for 30 days.

The amount of F- accumulated in brain, heart, thymus, kidney, testes, adrenal and femur of the F–fed group was significantly higher than those of controls.

J TOKYO MED COLL; 39 (3). 1981. 441-460.

Hygienic study on fluoride: 4. Physiological effects of fluoride on rat.

Tomomatsu T

Dep. Biochem., Tokyo Med. Coll.

Toxline abstract available at Toxnet



Case reports are presented of 8 patients with end stage renal disease who while undergoing dialysis received IV, excessive amounts of fluoride due to an unreported spill of hydrofluosilicic acid into the public water supply caused by cross connections in a treatment plant…

One patient upon autopsy was found to have high fluoride levels in lung tissue (5.6 ppm), kidney (7.0 ppm), brain (0.9 ppm) and blood (4.9 ppm).

Morb. Mortal. Wkly. Rep.; VOL 29 ISS Mar 28 1980, P134-136

Fluoride intoxication in a dialysis unit–Maryland

Anderson R, Beard JH, Sorley D

Bureau of State Services, and the Chronic Diseases Div., Field Services Div., Bureau of Epidemiology, Cent. for Disease Control, Atlanta, GA 30333


A wide variety of symptoms are encountered in chronic (human, animal) fluorosis. The soft tissue organs affected by F- are named in the following order: aorta, thyroid gland, lungs, kidneys, heart, pancreas, brain, spleen and liver. With advancing age their F- content increases.

Inhalation of fluoride produces foci of demyelinization in the cortex and in subcortical areas and a decrease in the number of Purkinje cells in the cerebellum.

FLUORIDE; 12 (3). 1978 111-114

Nonskeletal fluorosis.




150 ppm

The fluoride treatment decreased ascorbic acid concentration in the heart, spleen, brain, gizzard, pancreas and pectoralis, while it elevated levels in lung and kidney.

Excerpt: “The sharp decrease in the vitaimin level shown in the brain of the experimental birds could indicate depletion of the vitamin arising from stresses caused by fluoride treatment.”

FLUORIDE; 11 (2). 1978 60-67

The effects of fluoride on the growth and L-ascorbic acid levels of tissues from the domestic chicken (Gallus domesticus).

Yu MH, Driver CJ

Huxley Coll. Environ. Stud., West. Wash. Univ., Bellingham, Wash. 98225, USA.



The effect of prolonged administration of NaF on the metabolism of (guinea pig) Purkinje cells in the cerebellar cortex was studied by histochemical methods. Experimentation showed an intensification of the metabolic activity of the mitochondria and probably of the membrane system of the endoplasmic reticulum, activation of the complex of enzymes connected with active transport through membrane structures of cells and the absence of perceptible changes in the process of protein synthesis in experimental animals as compared with controls. Folia Histochem Cytochem (Krakow) 1974;12(1):37-44

Histochemical studies on the effect of sodium fluoride on metabolism in Purkinje’s cells.Czechowicz K, Osada A, Slesak B.

Toxline abstract available at Toxnet

Suggest NRC translate


Fluorosis patients

Neurological symptomatology in the form of the syndrome of vegetative-vascular dysfunction, or the asthenovegetative syndrome with polyneuritic (sensory and vegetative) disorders was detected in 78.8% of patients with occupational fluorosis in preosteal and osteal stages. Clinical and physiological investigations of the nervous system (psycho-physiological procedures, EEG, chronaximetry) showed patients with fluorosis to exhibit disturbed higher nervous activity and dysfunction of subcorticalaxial nonspecific structures of the brain.

GIG TR PROF ZABOL; (5). 1974 25-27

Aspects of nervous system affections in occupational fluorosis.


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1972 No abstract available

JAP J PHARMACOL; 22 (SUPPL). 1972 82



1971 Sodium fluoride activates adenyl cyclase at a rate that is dependent on temperature and the concentration of NaF. The activation is not readily reversed by dilution, extensive washing of the membrane-bound enzyme, or dialysis. Activation occurs in the absence of added Mg++, but the rate of activation is increased 2-fold by 5 mg Mg++…

J Biol Chem 1971 Jan 10;246(1):62-8

Adenyl cyclase of rat cerebral cortex. Activation of sodium fluoride and detergents.

Perkins JP, Moore MM.

*Available also at http://www.fluoridealert.org/wp-content/pesticides/nrc.brain.april.2004.htm