title: Gastric bypass in rats does not decrease appetitive behavior towards sweet or fatty fluids despite blunting preferential intake of sugar and fat.
abstract: After Roux-en-Y gastric bypass (RYGB) surgery, patients report consuming fewer fatty and dessert-like foods, and rats display blunted sugar and fat preferences. Here we used a progressive ratio (PR) task in our rat model to explicitly test whether RYGB decreases the willingness of rats to work for very small amounts of preferred sugar- and/or fat-containing fluids. In each of two studies, two groups of rats - one maintained on a high-fat diet (HFD) and standard chow (CHOW) and one given CHOW alone - were trained while water-deprived to work for water or either Ensure or 1.0M sucrose on increasingly difficult operant schedules. When tested before surgery while nondeprived, HFD rats had lower PR breakpoints (number of operant responses in the last reinforced ratio) for sucrose, but not for Ensure, than CHOW rats. After surgery, at no time did rats given RYGB show lower breakpoints than SHAM rats for Ensure, sucrose, or when 5% Intralipid served postoperatively as the reinforcer. Nevertheless, RYGB rats showed blunted preferences for these caloric fluids versus water in 2-bottle preference tests. Importantly, although the Intralipid and sucrose preferences of RYGB rats decreased further over time, subsequent breakpoints for them were not significantly impacted. Collectively, these data suggest that the observed lower preferences for normally palatable fluids after RYGB in rats may reflect a learned adjustment to altered postingestive feedback rather than a dampening of the reinforcing taste characteristics of such stimuli as measured by the PR task in which postingestive stimulation is negligible.
authors: Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, USA.
authors: Clare M
authors: CM
authors: Mathes
authors: Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, USA.
authors: Ryan A
authors: RA
authors: Bohnenkamp
authors: Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, USA.
authors: Ginger D
authors: GD
authors: Blonde
authors: Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, USA.
authors: Chanel
authors: C
authors: Letourneau
authors: Institute of Veterinary Physiology, Vetsuisse Faculty University of Zurich, Switzerland.
authors: Caroline
authors: C
authors: Corteville
authors: Institute of Veterinary Physiology, Vetsuisse Faculty University of Zurich, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, Switzerland.
authors: Marco
authors: M
authors: Bueter
authors: Institute of Veterinary Physiology, Vetsuisse Faculty University of Zurich, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, Switzerland; Institute of Laboratory Animal Science, Vetsuisse Faculty University of Zurich, Switzerland.
authors: Thomas A
authors: TA
authors: Lutz
authors: Diabetes Complications Research Centre, School of Medicine and Medical Science, University College Dublin, Ireland; Investigative Medicine, Imperial College London, UK; Gastrosurgical Laboratory, University of Gothenburg, Sweden.
authors: Carel W
authors: CW
authors: le Roux
authors: Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL, USA. Electronic address: spector@psy.fsu.edu.
authors: Alan C
authors: AC
authors: Spector
mesh_terms: D000821:Animal Feed; D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D003216:Conditioning, Operant / Q000502:physiology; D059305:Diet, High-Fat; D004041:Dietary Fats / Q000008:administration & dosage; D019422:Dietary Sucrose / Q000008:administration & dosage; D060766:Drinking Water / Q000008:administration & dosage; D004655:Emulsions / Q000008:administration & dosage; D002149:Energy Intake / Q000502:physiology; D005518:Food Preferences / Q000502:physiology; D005526:Food, Formulated; D015390:Gastric Bypass / Q000523:psychology*; D008297:Male; D023421:Models, Animal; D010743:Phospholipids / Q000008:administration & dosage; D011184:Postoperative Period; D017207:Rats, Sprague-Dawley; D012055:Reinforcement Schedule; D012201:Reward; D013024:Soybean Oil / Q000008:administration & dosage
chemical_list: D004041:Dietary Fats; D019422:Dietary Sucrose; D060766:Drinking Water; D004655:Emulsions; D010743:Phospholipids; C545823:soybean oil, phospholipid emulsion; C082131:Ensure formulated food; D013024:Soybean Oil
keywords: Bariatric surgery; Motivation; Operant behavior; Progressive ratio; Reward