Neem Leaf Supplement Ameliorates Depressive Like Behaviour in Alzheimer’s Disease Model in Adult Male Wistar Rats

Abstract

Aim of the Study: Currently, reports linked neuropathological changes in Alzheimer’s Disease (AD) to be a risk factor in depression. There is a need to develop natural therapeutics, with strong antioxidant property like Neem leaf, to avert AD’s neuropathological and behavioural changes using animal model induced by neurotoxin aluminium chloride. This study is aimed at ascertaining depressive like disorders in AD model while evaluating mechanism through which Neem averts AD neurodegeneration in the fronto-cerebellar cortex and possible depressive like behaviour. Methodology: Twenty (20) adult male Wistar rats used were grouped (n=5) viz: control group (A), neurodegenerative model given aluminium (B), 200mg/kg Neem leaf supplement (C) and 200mg/kg Neem leaf treated AD model (D). Neurobehavioural changes for reward memory and depressive like behaviour were evaluated using Y-maze (open arm reward test) and the tail suspension test (TST).  The frontal and cerebellar cortices were excised, fixed and processed for  Haematoxylin and Eosin stain (H and E), Cresyl fast violet (CFV) stain for Nissl bodies and astrocytes immunohistochemistry using glial fibrillary acidic protein (GFAP). Behavioural test data were analyzed using ANOVA and test for significance done @ p<0.05. Results: Aluminum induced neurodegeneration similar to AD pathology characterized by loss of neurons, chromatolysis, proliferation of astrocytes and decline in cognitive function in addition to exhibiting depressive like behaviour seen in a decrease number of reward arm entries, increase in time spent to reach reward arm and immobility time in the TST attributed to loss of cognitive function relative to loss of neurons integrity in the fronto-cerebellar cortex. However, neem leaf supplementation mitigates against AD model neuropathological and neurobehavioural  presentations resulting in an improved neurocognition, neuron survival or repair, decline in astrocytes proliferation and decline in depressive like behavior as compared to Aluminum induced AD model. Conclusion: Neem leaf alleviates depressive like behaviour associated with neurocognitive impairment through the interaction between neuron-astrocytes to protect neurons against aluminum induced neuroinflamamation and strengthens neural circuit for cognitive function.