Differential fructose and glucose appetition in DBA/2, 129P3 and C57BL/6 × 129P3 hybrid mice revealed by sugar versus non-nutritive sweetener tests

Inbred mouse strains differ in their postoral appetite stimulating response (appetition) to fructose as demonstrated in intragastric (IG) sugar conditioning and oral sugar vs. nonnutritive conditioning experiments. For example, FVB and SWR strains show experience-induced preferences for 8% fructose over a 0.1% sucralose + 0.1% saccharin (S + S) solution, whereas C57BL/6 (B6) and BALB/c strains do not. All strains, however, learn to prefer 8% glucose to S + S after experience, which is attributed to the potent appetition actions of this sugar. The present study extended this analysis to DBA/2 (DBA) and 129P3 (129) inbred mice. In Experiment 1A, ad libitum fed DBA and 129 mice preferred S + S to fructose before and after separate experience with the two sweeteners, indicating an indifference to the postoral nutrient effects of the sugar. When food restricted (Experiment 1B), 129 mice continued to prefer S + S to fructose while DBA mice showed equal preference for the sweeteners after experience, indicating some sensitivity to fructose appetition. In Experiment 1C, both strains acquired significant preferences for glucose over S + S after experience, confirming their sensitivity to postoral glucose appetition. Experiment 2 revealed that C57BL/6 × 129P3 (B6:129) hybrid mice responded like inbred B6 mice and 129 mice in acquiring a preference for glucose but not fructose over S + S. This is of interest because sweet "taste-blind" P2 × 2 / P2 × 3 double-knockout (DKO) mice on a B6:129 genetic background prefer fructose to water in 24 h tests, which is indicative of fructose appetition. Whether differences in the genetic makeup of DKO and B6:129 hybrid mice or other factors explain the fructose appetition of the DKO mice remains to be determined.