Effects of sodium overload on memory parameters and oxidative status of rat brain cortex

Abstract

The effects of sodium overload on learning and memory parameters of model animals are disputable. Additionally, it has been proved that brain oxidative stress leads to disrupted cognitive abilities. The aim of our study was to estimate the learning abilities and the oxidative status of brain cortices of rats in a model of sodium overload. In our experimental part two groups of male Wistar albino rats, receiving standard rodent food, were used – a Control group (C) and a NaCl group (NaCl), receiving 2.5 g/kg NaCl, p.o. once daily, for one week. After developing the sodium overload model, both groups were tested for their 8-Arm Radial Maze (8-ARM) performance. All rat brain cortices were tested for activity of Xanthine oxidase and free radical accumulation, using spectrophotometric methods. The results for group NaCl were presented as percentages of the corresponding biomarkers for group C. Group C showed much less anxiety and unmotivated behavior and considerably better memory and learning abilities than group NaCl. Much higher levels of xanthine oxidase and free radical accumulation were registered in the brain cortices of group NaCl compared to the brain cortices of group C. We discuss that the sodium overload resulted in oxidative stress in the rat brain cortex, mainly due to accumulation of superoxide. This was accompanied with increased anxiety, unmotivated choices, and disrupted learning and memory abilities. We concluded that excessive dietary NaCl intake in a rat model of sodium overload is accompanied by disrupted learning and memory abilities, increased anxiety and increased oxidative stress in the brain cortex.