title: Individual Differences in Cue-Induced Motivation and Striatal Systems in Rats Susceptible to Diet-Induced Obesity.
abstract: Pavlovian cues associated with junk-foods (caloric, highly sweet, and/or fatty foods), like the smell of brownies, can elicit craving to eat and increase the amount of food consumed. People who are more susceptible to these motivational effects of food cues may have a higher risk for becoming obese. Further, overconsumption of junk-foods leading to the development of obesity may itself heighten attraction to food cues. Here, we used a model of individual susceptibility to junk-foods diet-induced obesity to determine whether there are pre-existing and/or diet-induced increases in attraction to and motivation for sucrose-paired cues (ie, incentive salience or 'wanting'). We also assessed diet- vs obesity-associated alterations in mesolimbic function and receptor expression. We found that rats susceptible to diet-induced obesity displayed heightened conditioned approach prior to the development of obesity. In addition, after junk-food diet exposure, those rats that developed obesity also showed increased willingness to gain access to a sucrose cue. Heightened 'wanting' was not due to individual differences in the hedonic impact ('liking') of sucrose. Neurobiologically, Mu opioid receptor mRNA expression was lower in striatal 'hot-spots' that generate eating or hedonic impact only in those rats that became obese. In contrast, prolonged exposure to junk-food resulted in cross-sensitization to amphetamine-induced locomotion and downregulation of striatal D2R mRNA regardless of the development of obesity. Together these data shed light on individual differences in behavioral and neurobiological consequences of exposure to junk-food diets and the potential contribution of incentive sensitization in susceptible individuals to greater food cue-triggered motivation.
authors.affiliation: 1] Department of Psychology, University of Michigan, Ann Arbor, MI, USA [2] Department of Psychology, Wesleyan University, Middletown, CT, USA.
authors.forename: Mike J F
authors.initials: MJ
authors.lastname: Robinson
authors.affiliation: 1] Molecular and Behavioral Neuroscience Institute, The University of Michigan School of Medicine, Ann Arbor, MI, USA [2] Department of Psychiatry, University of Michigan School of Medicine, Ann Arbor, MI, USA.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Burghardt
authors.affiliation: Division of Metabolism, Endocrinology, and Diabetes, Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Christa M
authors.initials: CM
authors.lastname: Patterson
authors.affiliation: Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, MI, USA.
authors.forename: Cameron W
authors.initials: CW
authors.lastname: Nobile
authors.affiliation: Molecular and Behavioral Neuroscience Institute, The University of Michigan School of Medicine, Ann Arbor, MI, USA.
authors.forename: Huda
authors.initials: H
authors.lastname: Akil
authors.affiliation: Molecular and Behavioral Neuroscience Institute, The University of Michigan School of Medicine, Ann Arbor, MI, USA.
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Watson
authors.affiliation: Department of Psychology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Kent C
authors.initials: KC
authors.lastname: Berridge
authors.affiliation: Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, MI, USA.
authors.forename: Carrie R
authors.initials: CR
authors.lastname: Ferrario
mesh_terms: D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D003214:Conditioning, Classical; D003463:Cues; D004032:Diet / Q000009:adverse effects; D004198:Disease Susceptibility; D005215:Fasting; D007206:Individuality; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood; D008297:Male; D009042:Motivation / Q000502:physiology*; D009765:Obesity / Q000097:blood / Q000209:etiology / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011954:Receptors, Dopamine / Q000235:genetics / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism; D012054:Reinforcement, Psychology; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism
chemical_list: D007328:Insulin; D020738:Leptin; D011954:Receptors, Dopamine; D017450:Receptors, Opioid, mu; D000661:Amphetamine; D014446:Tyrosine 3-Monooxygenase