Drinking saccharin increases food intake and preference--II. Hydrational factors

Rats that drink saccharin solution increase their short-term food intake and develop a preference for flavored food eaten when saccharin is ingested. In this paper, we examined whether these changes in feeding behavior were due to overhydration resulting from drinking hyposmotic saccharin solution. Consistent with this possibility, the short-term food intake of rats was increased by drinking hyposmotic 0.2% saccharin dissolved in water, unaffected by drinking isosmotic 0.9% NaCl, and decreased by drinking 0.2% saccharin dissolved in 0.9% NaCl. In addition, rats showed a sustained increase in saccharin-induced food intake after antidiuretic hormone treatment, which was designed to exacerbate their positive water balance. Less consistent with a hydrational explanation of saccharin-induced feeding was the finding that rats drinking only 2ml 0.2% saccharin solution increased food intake. Also, gastric intubation of similar volumes of water produced a small, transient increase in feeding behavior, which was apparent after the first intubation only and could not be preserved by adding water-contingent flavors to the food. Taken together, these results suggest that the hydrational effects of drinking hyposmotic saccharin solution contribute to, but cannot account for, the increase in food intake. Hydration had no observable influence on the acquisition of flavored food preference.