Fructose- and glucose-conditioned preferences in FVB mice: strain differences in post-oral sugar appetition

Recent studies indicate that, unlike glucose, fructose has little or no post-oral preference conditioning actions in C57BL/6J (B6) mice. The present study determined whether this is also the case for FVB mice, which overconsume fructose relative to B6 mice. In experiment 1, FVB mice strongly preferred a noncaloric 0.1% sucralose + 0.1% saccharin (S+S) solution to 8% fructose in a 2-day choice test but switched their preference to fructose after separate experience with the two sweeteners. Other FVB mice displayed a stronger preference for 8% glucose over S+S. In a second experiment, ad libitum-fed FVB mice trained 24 h/day acquired a significant preference for a flavor (CS+) paired with intragastric (IG) self-infusions of 16% fructose over a different flavor (CS-) paired with IG water infusions. IG fructose infusions also conditioned flavor preferences in food-restricted FVB mice trained 1 h/day. IG infusions of 16% glucose conditioned stronger preferences in FVB mice trained 24- or 1 h/day. Thus, fructose has post-oral flavor conditioning effects in FVB mice, but these effects are less pronounced than those produced by glucose. Further studies of the differential post-oral conditioning effects of fructose and glucose in B6 and FVB mice should enhance our understanding of the physiological processes involved in sugar reward.