Effects of oleuropein on malondialdehyde level and expression of GluN2B gene following passive avoidance memory impairment in mice

Introduction: Oleuropein is the most important phenolic compound in olive leaves which has several pharmacological properties. So far, this compound has been shown to have antioxidant, anti-inflammatory, anti-atrogenic, antimicrobial, and antiviral properties. Scopolamine is a muscarinic antagonist used as standard medication for inducing cognitive deficits in humans and animals. This study was performed to investigate the effect of oleuropein on the function of passive avoidance memory, malondialdehyde level, and expression of GluN2B gene in the model of memory impairment caused by scopolamine.   Materials & Methods: In total, 35 male mice were randomly divided into five groups (n=7). The control group received normal saline, and the Sco (scopolamine) group received intraperitoneal scopolamine at a dose of 1 mg/kg for three weeks. The treatment groups received oleuropein in three doses of 5, 10, and 20 mg/kg. At the end of the shuttle box test, the brain tissues of the animals were removed for the determination of oxidative stress and molecular tests.   Findings: The results of our study showed that scopolamine significantly decreased memory and induced oxidative stress (P<0.05). On the other hand, oleuropein improved memory and learning and reduced oxidative damage (P<0.05). Oleuropein treatment reduced the elevated brain MDA levels in mice receiving scopolamine (P<0.05). Oleuropein at three doses used in this study did not significantly alter the expression of the GluN2B gene in the hippocampus (P>0.05).   Discussions & Conclusions: In general, the treatment of mice with oleuropein improved memory impairment due to dysfunction of the cholinergic system in the brain that may be due to the reduction in oxidative stress; moreover, it may be regarded as a method to manage neurological disorders in conditions of dementia.