Restricted Daily Feeding of Liquid Meal Reduces the Motivation of Rats to Get Food

To corroborate the hypothesis that mastication affects the motivation to get food, we examined the effects of dietary consistency on the development of meal anticipation in locomotor activity of rats subjected to restricted daily feeding (RF), in which food supply was restricted to a fixed time each day. RF of both liquid and solid meals produced anticipatory locomotor activity. However, the strength of the activity in rats subjected to RF of liquid meal was lower than that in rats subjected to RF of solid meal. These results suggest that the feeding-associated circadian oscillation that developed by feeding with liquid meal is less potent than that in the case of feeding with solid meal. Furthermore, mastication for digesting solid meal might be one of the factors that determine the strength of the feeding-associated circadian oscillation.