EFFECTS OF ALUMINIUM CHLORIDE ON THE HISTOLOGY OF THE CEREBRAL CORTEX, BRAIN ALUMINIUM UPTAKE AND BEHAVIOURAL ENDPOINTS OF ADULT WISTAR RATS

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Department of Medicine

ABSTRACT
Aluminium is presents in many manufactured foods, medicines and is also added to drinking water for purification purposes. Aluminium exposure and neurological impairments demonstrate mixed findings. The cerebral cortex is a sheet of neural tissue that is outer-most to the cerebrum of the mammalian brain and it plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. Anxiety is a general term for several disorders that cause nervousness, fear, apprehension and worrying. Anxiety affects one-eighth of the total population world-wide. The objectives of this study was to investigate the possible effects that aluminium chloride exposure could have on spatial learning and memory, anxiety-related behaviour, brain aluminium uptake, histology of cerebral cortex, body and brain weights of adult wistar rats. Fifty adult wistar rats were used for this study. The wistar rats were divided into five groups; group I was the control, group II received 475mg/Kg, group III received 950mg/kg, group IV received 1,425mg/kg and group V received 1,900mg/kg via oral intubation for a duration of eight weeks. The LD50 was 3,807kg/kg. Study of spatial learning and memory was done (measured) with the aid of Morris water maze while the elevated plus maze was used to study anxiety-like behaviour. Neutron activation analysis method (NAA) was used to determine the quantity (concentration) of aluminium uptake by the brain, while haematoxylin and eosin, as well as Hirano-Zimmerman stains were used for the histology of the cerebral cortex. The results of this study showed that on the Morris water maze, at the first run of training, the wistar rats in the control and aluminium treated groups got to the platform at different time as they were trying to learn tasks which were not statistically significant at P<0.05; But for the second and third runs (testing), we observed that wistar rats in the control group got to the platform faster than the aluminium treated groups which was statistically significant at P< 0.05 and this, implies that aluminium chloride impaired the spatial learning and memory of the wistar rats. Activities on the elevated plus maze showed that there was statistically significant increased rate of anxiety across the groups which were prominent among the aluminium treated groups. There was brain accumulation of aluminium in the aluminium treated rats and the histology of the cerebral cortex showed neuronal vacuolation and necrosis of the cerebral cortex in the aluminium treated groups when compared with the control.We also observed statistically significant decrease in the body weight but the brain weight loss observed was not statistically significant at P<0.05. Based on our observations, we therefore conclude that aluminum chloride exposure had negative effects on behavioral end points as manifested in impaired spatial learning and memory, and increase anxiety (affect anxiety-like behaviour); It also resulted into increased brain uptake (accumulation) of aluminium in the treated groups, caused neuronal vacuolation and necrosis of the cerebral cortex and caused weight loss in wistar rats.