Quercetin Ameliorate Oxidative/Nitrosative Stress in The Brain of Rats Exposed to Intermittent Hypobaric Hypoxia

High altitude exposure is an extreme physiological oxidative/nitrosative stress and the brain is more sensitive tissue of the body. Quercetin (Que) is a natural flavonoid abundant in fruits and vegetables. The present study investigated the brain region specific changes in striatum, hippocampus and cortex on oxidative/nitrosative stress markers and the effects of Que administration in rats exposed to intermittent hypobaric hypoxia (IHH). Wistar male rats were exposed to short-term (2 days) or long-term (4 weeks, 5 days/week) IHH in a hypobaric chamber. Half of the rats received Que (30 mg/kg body weight) daily, before each IHH exposure. Control rats were kept under normobaric normoxia (Nx) and treated in a corresponding manner. After the last exposure to IHH, the brain was removed and the oxidative/nitrosative stress markers were determined in the three parts of the brain (striatum, hippocampus and cortex) tissue homogenate: the free radicals (malondialdehyde, MDA and carbonylated proteins, CP), nitrite plus nitrate (NOx) production and activity of antioxidant enzymes (superoxide dismutase, SOD and catalase, CAT). Results indicate an increase in free radicals and NOx production and a decrease of the antioxidant defense system in all the three regions of the brain after IHH exposure. The Que treatment significantly lower the free radicals and NOx production and significantly higher the SOD and CAT levels in all the three brain regions after IHH exposure. The observation suggests that the hypoxia differentially affects the brain regions and Que provides substantial neuroprotection against IHH-induced oxidative/nitrosative damage.