Pre-existing differences in motivation for food and sensitivity to cocaine-induced locomotion in obesity-prone rats.
Physiol Behav
; 152(Pt A): 151-60, 2015 Dec 01.
Article
em En
| MEDLINE
| ID: mdl-26423787
ABSTRACT
Obesity is a significant problem in the United States, with roughly one third of adults having a body mass index (BMI) over thirty. Recent evidence from human studies suggests that pre-existing differences in the function of mesolimbic circuits that mediate motivational processes may promote obesity and hamper weight loss. However, few preclinical studies have examined pre-existing neurobehavioral differences related to the function of mesolimbic systems in models of individual susceptibility to obesity. Here, we used selectively bred obesity-prone and obesity-resistant rats to examine 1) the effect of a novel "junk-food" diet on the development of obesity and metabolic dysfunction, 2) over-consumption of "junk-food" in a free access procedure, 3) motivation for food using instrumental procedures, and 4) cocaine-induced locomotor activity as an index of general mesolimbic function. As expected, eating a sugary, fatty, "junk-food" diet exacerbated weight gain and increased fasted insulin levels only in obesity-prone rats. In addition, obesity-prone rats continued to over-consume junk-food during discrete access testing, even when this same food was freely available in the home cage. Furthermore, when asked to press a lever to obtain food in an instrumental task, rates of responding were enhanced in obesity-prone versus obesity-resistant rats. Finally, obesity-prone rats showed a stronger locomotor response to 15 mg/kg cocaine compared to obesity-resistant rats prior to any diet manipulation. This enhanced sensitivity to this dose of cocaine is indicative of basal differences in the function of mesolimbic circuits in obesity-prone rats. We speculate that pre-existing differences in motivational systems may contribute to over-consumption and enhanced motivation in susceptible individuals.
Palavras-chave
Texto completo:
1
Bases de dados:
MEDLINE
Assunto principal:
Cocaína
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Inibidores da Captação de Dopamina
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Comportamento Alimentar
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Motivação
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Atividade Motora
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Obesidade
Tipo de estudo:
Diagnostic_studies
Limite:
Animals
Idioma:
En
Revista:
Physiol Behav
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Estados Unidos