A microstructural analysis of water intake patterns associated with light phase food and water restriction in male and female rats.

Water intake is influenced by both eating and circadian rhythms, and the available literature is mixed regarding which variable exerts greater control. Previous reports primarily focused on short term manipulations, however, one study using long term light phase food restriction found that water intake patterns primarily retained circadian characteristics in male rats. To further characterize this behavioral effect, water intake and lick microstructure was analyzed in male and female rats with food access restricted to the light phase. In addition, food and water intake and lick microstructure were analyzed when water access was restricted to the light phase. In support of the previous short term, but not long term, food manipulation studies, when food access was restricted to the light phase most water intake shifted to this time frame. This shift was medicated by increased lick burst number, suggesting altered satiety signaling underling this intake pattern. When water access was restricted to the light phase, food intake was equally distributed across the light and dark phases. There was no effect of sex on the patterns of intake during any test condition. These results further our understanding of the mechanisms underlying food and water-associated and circadian intake patterns by suggesting that altered satiety signaling underlies changes in water intake. Furthermore, these results show that the timing of food access has a greater effect on water intake patterns across the light-dark cycle than water access has on food intake patterns.