Behavioral and Histopathological Improvement by Gallic Acid in Scopolamine-Induced Dementia: Mitigation of Oxidative Stress, Inflammation, and Cholinergic Impairment

Background: Gallic acid one of well-known natural phenolic compounds with antioxidant property that offers neuroprotective functions. Alzheimer’s disease a neurodegenerative disease that results in dementia in elderly peoples. The aim of this study to investigate the ameliorative effect of gallic acid on scopolamine-induced memory loss and cognitive impairment. Methods: The rats were divided into four groups (n-6): Control group, Gallic acid group, Scopolamine group, Scopolamine+gallic acid group. Behavioral testes, including Y-maze, water maize, and passive avoidance testes, were conducted a half hour after-scopolamine injection, oxidative damage indicators such as superoxide dismutase (SOD), malonaldehyde (MDA), catalase (CAT), reduced glutathione (GSH) were measured. Also, EIISA measurements for inflammatory cytokines interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and acetylcholine esterase (AchE) enzyme activity was performed in cortical tissues. Histological examination of cortical tissues was also performed. Results: Gallic acid significantly mitigated scopolamine-induced behavioral changes by decreasing entry latency and escape latency in water maize test. It also reduced lipid peroxidation (MDA), and cortical inflammatory markers (TNF-α, IL-1β, IL-6,) and decreased AchE enzyme activity. Conversely, gallic acid significantly increased the spontaneous alternation%, and step-through latency in Y- maze and passive avoidance tests. Additionally, gallic acid elevated the level of antioxidant defense components (SOD, CAT, GSH).and increased the number of healthy neurons in cortical tissues. Conclusions: The finding of our study explored the novel neuroprotective effect of gallic acid against scopolamine-induced memory affection through its antioxidant, anti-inflammatory effects, and its inhibitory effect on AchE enzyme.