K. Ackroff et al., Flavor preferences conditioned by intragastric fructose and glucose - Differences in reinforcement potency, PHYSL BEHAV, 72(5), 2001, pp. 691-703
Many prior conditioning studies indicate that fructose, unlike glucose, has
minimal postingestive reinforcing effects. Using a new training procedure,
food-restricted rats were trained in alternate 20-h/day sessions with one
flavored solution (CS+F) paired with intragastric Od) infusions of 16% fruc
tose and another flavor (CS-) paired with IG water. In subsequent two-bottl
e tests they showed a robust (85%) preference for the CS+F over the CS-. A
third flavor (CS+G) was then paired with IG 16% glucose, and it was strongl
y preferred to the CS+F. When retrained 30 min/day with new flavors paired
with IG fructose, glucose, or water the rats learned only a CS+G preference
. When training was extended to 20 h/day, a CS+F preference developed. New
rats trained 20 h/day with two-bottle access to CS+F and CS- paired with IG
fructose and water failed to acquire a CS+F preference. Other rats rapidly
developed a strong preference when trained with concurrent access to CS+G
and CS- paired with IG glucose and water. These data indicate that both fru
ctose and glucose generate postingestive reinforcing signals, but that the
fructose signals are weaker and/or delayed relative to those produced by gl
ucose. (C) 2001 Elsevier Science Inc. All rights reserved.