Antioxidant mechanisms in neuroprotective action of lipoic acid on learning and memory of rats with experimental dementia

摘要: Alzheimer's disease (AD) is one of the most common dementia affecting about 36 million people and without effective cure. Oxidative stress is one of many hypotheses for the AD mechanisms. Possible preventive AD effects of some antioxidants continue to be the object of clinic and experimental research. The aim of this study was to evaluate the antioxidant mechanism in the neuroprotective effect of lipoic acid (LA) on the cognitive functions in experimental dementia. Alzheimer's disease type dementia was produced via scopolamine treatment (Sco, 1 mg/kg ip, 11 days) on male Wistar rats. Lipoic acid (LA, 30 mg/kg, ip) was applied for the same period. Learning and memory performance of the rats were evaluated using passive avoidance learning test (Step through test). At the 24th hour after the last treatment the brain frontal cortex, hippocampus, and striatum were isolated and homogenized. The homogenates were used for determination of malondialdehyde (MDA), total glutathione (tGSH), and activities of superoxide dismutase (SOD), glutathione peroxidase and catalase (CAT). The dementia model was verified by the cognitive tests used. In brain structures of the Sco-group increased MDA, and decreased tGSH levels, as well as activated antioxidant enzymes were observed. LA significantly improved cognitive functions and oxidative status damaged by Sco by increased tGSH level, restored CAT and SOD activities. Thus LA significantly protects memory impairments of dement animals due to its antioxidant capacity and could be used in prevention and therapy of AD.