Flavor preferences conditioned by intragastric fructose and glucose: differences in reinforcement potency.
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 (IG) infusions of 16% fructose and another flavor (CS-) paired with IG water. In subsequent two-bottle 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 strongly 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 fructose and glucose generate postingestive reinforcing signals, but that the fructose signals are weaker and/or delayed relative to those produced by glucose.
Ackroff
K
K
Department of Psychology, Brooklyn College of the City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA. kackroff@gc.cuny.edu
Touzani
K
K
Peets
T K
TK
Sclafani
A
A
D000818:Animals; D003216:Conditioning, Operant; D005260:Female; D005518:Food Preferences / Q000187:drug effects*; D005632:Fructose / Q000008:administration & dosage / Q000494:pharmacology*; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D007441:Intubation, Gastrointestinal; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D013649:Taste / Q000187:drug effects*
D005632:Fructose; D005947:Glucose