Food ingestion is more important to plasma corticosterone dynamics than water intake in rats under restricted daily feeding

Abstract

The roles of food and/or water ingestion in the regulation of plasma corticosterone level were examined in rats under restricted daily feeding. When the time of food-pellets and water supply was restricted to 2 hours in the early light period (meal feeding) for 2 weeks, the corticosterone level increased prior to meal (prefeeding peak). A similar prefeeding hormone peak was observed when supply of food-pellets was restricted to 2 hours with free-access to water (food restriction). In contrast, when water supply was restricted to 2 hours with free-access to food-pellets (water restriction), the hormone level before water supply did not increase as much as that under meal feeding or food restriction. Shortening of an available time for water under water restriction or prolongation of the restriction schedule failed to elevate the hormone level furthermore. On the other hand, the high prefeeding corticosterone level before meal decreased subsequently to meal feeding (prandial fall), which was not observed when rats were kept fasting during the meal time. This prandial fall of the hormone level was not observed by water intake alone, and closely related to food-pellets ingestion. It is concluded that food ingestion is more important than water intake to the formation of the prefeeding corticosterone peak and to the prandial fall of the hormone level under restricted daily feeding.