Sprague Dawley albino rats were treated with 30, 45, and 75 mg NaF/kg body weight/day respectively for 20 days and 35 days to study neurotoxic effect of fluoride. The control rats were injected with double distilled water 1cc/kg body weight/day. The animals were sacrificed and the cerebrum was analysed for neurodegenerative anomalies. The adenomatous foci were formed in the cerebral cortex containing degenerating glial cells. The glial cells became vacuolated and showed hyperchromatization of

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... chromatization of nuclei in brain of rats treated with 30 mg NaF/kg body weight/day. The chain formation of the disintegrated glial cells, senile plaque and large globose shaped neurofibillary tangle inside the perikaryon in cerebral cortex were observed in rats treated with 45 mg NaF/kg body weight/day. An elongated highly chromatolytic region with large number of vacuolated cells was visible. In some neurons, neuroplasm become hyperchromatic, fragmentation and apoptosis of nuclei was prominent. Pleomorphic, irregular glial cells showed necrosis, the cerebral cortex exhibited diffused haemorrhages in rats of 75 mg NaF dose group. The results of present study revealed a fairly consistent pattern of adverse effects by fluoride on cerebral neuropathology, which may be a cause of neurological sequelae and abnormal neuro-behavioural patterns in fluorosis. INTRODUCTION Fluoride has the ability to interfare with the functions of the brain that causes impairment of central nervous system (Bhatnagar et al., 2002). zFluoride produces neuronal destructions (Bhatnagar et al., 2006; Blaylock, 2004) and synaptic injury by a mechanism that involves free redical production and lipid peroxidation (Byers et al., 2005). Substantial cell loss in brain structures associated with dementia, in the neocortex and hippocampus has been reported in fluoride treated rats (Guo et al., 2008). Wang et al., (Kluver and Barrera, 1953) investigated the effect of fluoride on learning and memory ability of the offspring rats and concluded that learning and memory were increasingly disturbed by exposure to high fluoride. The rats chronically exposed in vitro to methane sulphonyl fluoride displayed marked sex specific differences in morphological development of the cerebral cortical layer (Liu, 1989). Fore brain size and cortical thickness were increased in females and decreased in males. Recent evidances indicate that fluoride induces depletion of mucosubstances and DNA damage and apoptosis in rat brain cortical slices (Lu et al., 2000; Mullenix et al., 1995). The present study has been designed to assess the neurotoxic effect of fluoride on cerebrum of rat exposed to 30, 45, and 75 mg NaF/kg body weight/day for 20 and 35 days respectively.