Influence of excessive sucrose consumption on exploratory behaviour in rats - Possible implications for the brain reward system

Due to the low cost of production and the strong evolutionary preference for sweet taste in humans, sugar is added to many food products. This leads to often involuntary overconsumption of high amounts of sugar. Yet, growing evidence indicates that high-sugar diets impact brain function and impair cognitive ability. It may be due to physiological changes in specific regions of the brain or/and maladaptive changes in dopamine signalling similar to those observed in the etiology of addiction. In our study, rats from the experimental group were kept on a feeding protocol involving intermittent access to sucrose solution for eight weeks. Then, the animals underwent a spontaneous exploration test in an experimental arena divided into three zones where stationary and movable objects were placed. Studying the rats' exploratory behaviour allowed us to assess the impact of the sucrose diet on a broad spectrum of behaviours related to the general functioning of the organism in its environment. Analyses showed differences in reaction to novelty between different diet groups which had been placed in different experimental setups. Rats from the sugar-fed group responded to change with more pronounced exploratory behaviours directed at the source of the novel stimuli and the surrounding environment. These results may indicate a lower reward value of novelty resulting from diminished responsiveness of the reward system in the sugar-diet group. We have not found evidence for memory and/or learning impairments in rats on the sugar-rich diet.