Cognitive Ability, Activity and Metabolic Rate in Mice Divergent for Water Consumption

Physical activity is known to not only affect the physical health of the body but mental and cognitive health as well. Exercise is favorably correlated with cognition, improving memory, and delayed age related memory decline. Furthermore, low water consumption has been associated with cognitive issues. Two inbred mouse strains divergent for water consumption, C57 Brown/cdj (BR) and C57 Black/10J (BL), were evaluated as a part of a larger study to identify genes associated with water consumption. Physical activity and cognition have not been studied in these strains; however, we have anecdotally observed greater activity and more elaborate nest building in BR mice. The objective of the present study was to investigate differences between the two strains in physical activity, metabolic rate and cognition. Physical activity and metabolic rate (n = 16), water consumption (n=76), and cognition (n=32) were measured in males and females of each line and fitted to a general linear model including the effects of mouse strain. Physical activity and metabolic rates were measured in males between 4 and 6 wk of age using Sable Promethion chambers. Energy expenditure (P<0.0001), activity (P<0.10) and metabolic rate measured as carbon dioxide expenditure (P<0.05) were all higher in BR than BL animals. Daily water consumption data were collected for four days during the 4^th, 5^th, and 6^th wk by using custom water bottles. Animals were weighed at the beginning of the 4^th, 5^th, and 6^th wk, and at the end of the 6^th wk. Consumption data were corrected for metabolic body weight (wt^0.67) prior to analysis, so units of water consumption are expressed in milliliters consumed per gram of metabolic body weight per day. Animals from the BR strain consumed more water per day (P<0.001) than BL animals (1.32 vs 0.65 ml/g, respectively). Cognition was examined by evaluating the likelihood of an animal successfully entering the correct escape hole in a Barnes maze by using a generalized linear model including the effects of sex and strain. Females were more likely to complete the maze within 5 min (P<0.10) than their male counterparts (82% vs 69% success rate of completion, respectively). The completion rate for BR was higher (P<0.10) than that for BL, 87% vs 61%, respectively. These results support the hypothesis of favorable relationships between activity, water consumption and cognition.