Post-oral infusion sites that support glucose-conditioned flavor preferences in rats.
Rats learn to prefer a flavored solution (CS+) paired with a gastrointestinal glucose infusion over an alternate flavor (CS-) paired with a non-caloric infusion. Prior work implicates a post-gastric site of glucose action, which is the focus of this study. In Exp. 1, male rats (8-10/group) were infused in the duodenum (ID), mid-jejunum (IJ), or distal ileum (II) with 8% glucose or water as they drank saccharin-sweetened CS+ and CS- solutions, respectively, in one-bottle 30-min sessions. Two-bottle tests (no infusions) were followed by a second train-test cycle. By the second test, the ID and IJ groups preferred the CS+ (69%, 67%) to the CS- but the II group did not (48%). Satiation tests showed that ID and IJ infusions of glucose reduced intake of a palatable solution similarly, while II infusions were ineffective. In Exp. 2, rats (10/group) drank CS solutions in one-bottle, 30-min sessions and were given 2-h ID or hepatic portal vein (HP) infusions. The CS+ and CS- were paired with 10 ml infusions of 10% glucose and 0.9% saline, respectively. Following 8 training sessions, the ID group preferred the CS+ (67%) to the CS- but the HP group did not (47%) in a two-bottle test. The similar CS+ preferences displayed by ID and IJ, but not II groups implicate the jejunum as a critical site for glucose-conditioned preferences. A pre-absorptive glucose action is indicated by the CS+ preference displayed by ID but not HP rats in Exp. 2. Our data were obtained with non-nutritive CS solutions. HP glucose infusions are reported to condition preferences for a flavored food that itself has pre- and post-absorptive actions. Thus, there may be multiple sites for glucose conditioning with the upper or mid-intestines being the first site of action.
Ackroff
Karen
K
Department of Psychology, Brooklyn College, 2900 Bedford Avenue, Brooklyn, New York 11210, USA. kackroff@gc.cuny.edu
Yiin
Yeh-Min
YM
Sclafani
Anthony
A
D000818:Animals; D003214:Conditioning, Classical / Q000187:drug effects*; D004386:Duodenum / Q000502:physiology*; D005518:Food Preferences; D005947:Glucose / Q000008:administration & dosage* / Q000494:pharmacology; D007082:Ileum / Q000502:physiology*; D007262:Infusions, Intravenous / Q000523:psychology; D007441:Intubation, Gastrointestinal / Q000523:psychology; D007583:Jejunum / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology
D005947:Glucose