Drinking saccharin increases food intake and preference--III. Sensory and associative factors

Rats that drink saccharin solution increase their short-term food intake and develop a preference for flavored food eaten when saccharin is ingested. Here we describe experiments that examined whether these changes in feeding behavior were due to learning and/or the reinforcing sensory properties of saccharin solution. It was found that learning was unnecessary for the feeding response, as rats that drank saccharin increased food intake whether or not their food contained saccharin-contingent flavor cues. However, learning helped support and maintain the response, as rats repeatedly given flavored food together with saccharin to drink later increased intake when given the flavored food without saccharin (i.e. in extinction). The rewarding or hedonic effects of the immediate orosensory properties of saccharin were not responsible for its effects on feeding, as drinking saccharin before but not after eating flavored food increased food intake and food preference. Furthermore, hungry rats developed an aversion to flavored food paired with saccharin ingestion when the quantity of food was limited. This implies that the flavored food preference produced by drinking saccharin involves an association between sensory aspects of the food and the metabolic consequences of food ingestion, which interact with a postingestive action of drinking saccharin that is related to the rat's metabolic state.