Beneficial effects of environmental enrichment and food entrainment in the R6/2 mouse model of Huntington's disease

Abstract

Background: In addition to their cognitive and motor deficits, R6/2 mice show a progressive disintegration in circadian rhythms that mirrors the problems associated with sleep-wake disturbances experienced by patients with Huntington's disease (HD). It has been shown previously that motor and cognitive performance, as well as survival, can be improved in transgenic mouse models of HD through the provision of environmental enrichment. Methods: We compared the effect of two different overnight entrainment paradigms presented either separately or in combination. The first was environmental enrichment, the second was temporal food-entrainment. Environmental enrichment was provided in the dark period (the natural active period for mice) in the form of access to a Perspex playground containing running wheels, tunnels, climbing frame, ropes and chew blocks. Food entrainment was imposed by allowing access to food only during the dark period. We assessed a number of different aspects of function in the mice, measuring general health (by SHIRPA testing, body temperature and body weight measurements), cognitive performance in the touchscreen and locomotor behavior in the open field. Results: There were no significant differences in cognitive performance between groups on different schedules. Environmental enrichment delayed the onset of general health deterioration, while food entrainment slowed the loss of body weight, aided the maintenance of body temperature and improved locomotor behavior. Effects were limited however, and in combination had deleterious effects on survival. Conclusions: Our results support previous studies showing that environmental enrichment can be beneficial and might be used to enhance the quality of life of HD patients. However, improvements are selective and 'enrichment' per se is likely to only be useful as an adjunct to a more direct therapy. It has been shown previously that motor and cognitive performance, as well as survival, can be improved in transgenic mouse models of HD through the provision of environmental enrichment. Here, we compared the effect of two different overnight entrainment paradigms presented either separately or in combination. While there were no significant differences in cognitive performance between groups on different schedules, environmental enrichment delayed the onset of general health deterioration, whereas food entrainment slowed the loss of body weight, aided the maintenance of body temperature, and improved locomotor behavior.