The Effect of Quercetin on Learning and Memory Deficit, Lipid Peroxidation, and Cholinesterase Activeity Following Lipopolysaccharide in the Rat

Lipolysaccharide (LPS) is a large molecule isolated from bacteria such as the enterobacteriaceae family with a negative effect on memory and learning through disturbing the balance of free radicals and creating oxidative stress conditions. In this study, we evaluated  the effect of quercetin on oxidative stress and LPS-induced memory impairment in the rat. Male rats (n=40) were randomly divided into 5 groups: control, control under treatment with quercetin at a dose of 50 mg/kg, LPS, and LPS groups treated with quercetin at doses of 10 or 50 mg/kg. For induction of inflammation, LPS dissolved in normal saline (500 μg/kg) was injected intraperitoneally. After one week, the passive avoidance behavior was tested in the shuttle box and hippocampal homogenate was prepared. Acetylcholinesterase (AChE) activity and lipid peroxidation (malondialdehyde, MDA) were measured using specific kits. Data were analyzed by SPSS software (version 16). Step-through latency (STL) in quercetin50-treated LPS group was significantly greater than control group (p<0.05). In addition, AChE activity and level of MDA was significantly lower in quercetin50-treated LPS group versus LPS group (p<0.05). Meanwhile, quercetin at a dose of 10 mg/kg did not have such a significant effect. Quercetin at a dose of 50 mg/kg has a protective effect on learning and memory impairment due to LPS and part of its beneficial effect is mediated via attenuation of lipid peroxidation and AChE.