BALB/c and SWR inbred mice differ in post-oral fructose appetition as revealed by sugar versus non-nutritive sweetener tests

Recent studies indicate that C57BL/6J (B6) and FVB inbred mouse strains differ in post-oral fructose conditioning. This was demonstrated by their differential flavor conditioning response to intragastric fructose and their preference for fructose versus a non-nutritive sweetener. The present study extended this analysis to SWR and BALB/c inbred strains which are of interest because they both show robust flavor conditioning responses to fructose. In the first experiment, ad-libitum fed mice were given a series of 2-day, two-bottle preference tests between 8% fructose and a more preferred, but non-nutritive 0.1% sucralose + 0.1% saccharin (S + S) solution (tests 1 & 4), and fructose or S + S versus water (tests 2 and 3). In test 1, SWR mice preferred S + S to fructose, and in tests 2 and 3, they preferred both sweeteners to water. In test 4, SWR mice switched their preference and consumed more fructose than S + S. In contrast, ad-libitum fed BALB/c mice strongly preferred S + S to fructose in both tests 1 and 4, although they preferred both sweeteners to water in tests 2 and 3. Food-restricted BALB/c mice also preferred the non-nutritive S + S to fructose in tests 1 and 4. The experience-induced fructose preference reversal observed in SWR, but not BALB/c mice indicates that fructose has a post-oral reinforcing effect in SWR mice as in FVB mice. Because B6 and FVB mice prefer glucose to fructose based on the post-oral actions of the two sugars, the second experiment compared the preferences of SWR and BALB/c mice for 8% glucose and fructose solutions. Ad-libitum fed and food-restricted SWR mice strongly preferred glucose to fructose. In contrast, ad-libitum fed BALB/c mice were indifferent to the sugars, perhaps because of their overall low intakes. Food-restricted BALB/c mice, however, strongly preferred glucose. These findings indicate that SWR and BALB/c mice differ in their preference response to the post-oral actions of fructose.