The protective role of melatonin on the brain in a rat model of Alzheimer's disease.

Alzheimer's disease is an age-related neurodegenerative disorder characterized by progressive cognitive decline and multiple biochemical and structural abnormalities in the brain. Accumulating evidence suggests that aluminum exposure may contribute to neurodegenerative process including those observed in AD and was linked to neuronal damage and cognitive impairment. Melatonin (Mel) is a neurohormone that regulates circadian rhythm and possesses antioxidant, anti-inflammatory and neuroprotective properties. The current study investigated the potential protective roles of Mel in a rat model of AD induced by aluminum chloride (AlCl3). Forty adult male rats were divided into 4 experimental groups: a control group, an AlCl3-treated group, an AlCl3+Mel-treated group, and a Mel-only group. AlCl3 was administered orally for four weeks. Cognitive performance and spatial learning were assessed using Morris water maze test. Plasma levels of the pro inflammatory cytokines; interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) were measured using enzyme linked immunosorbent assay. Histopathological examination of the frontal cortex was performed using hematoxylin and eosin staining, and immunohistochemistry was conducted using the neuronal marker NeuN, microglial marker Iba1, and inflammatory markers IL-6 and TNF-α. Mel treatment significantly improved learning and memory performance in the Morris water maze test. It also reduced plasma levels of IL-6 and TNF-α. Using immunohistochemistry, Mel increased NeuN expression, while reducing Iba1, IL-6 and TNF-α expression. These findings showed that Mel attenuated frontal cortical neurodegeneration and neuroinflammation in this model of AD, suggesting that Mel may represent a promising neuroprotective therapeutic strategy for AD.