Date of Award

Spring 2025

Document Type

Restricted Thesis

Terms of Use

© 2025 Steven Gooden. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts

Department

Psychology Department

First Advisor

Wambura Fobbs

Abstract

Although dieting is promoted as an effective weight management strategy, long-term dieting success is low, and many people relapse to unhealthy eating patterns in response to brief re-exposure to palatable foods or stress. Here, we used an adapted reinstatement model (commonly used to study relapse to drugs of abuse) to determine whether food priming or a pharmacological stressor triggers the reinstatement of palatable food seeking behavior in male and female mice. Mice were food restricted to 90% of their free-feeding body weight and trained to self administer palatable food pellets (calorically dense and rich in sugar) on a fixed-ratio 1 with 20-sec timeout reinforcement schedule during 3-hour sessions 6 days per week for 2.5 weeks. After self-administration training, mice underwent extinction training (during which nose pokes were not reinforced). We then assessed the reinstatement of food seeking behavior following pellet-priming (i.e., non-contingent pre-session delivery of food pellets) or the administration of yohimbine (an α2-adrenoceptor antagonist that promotes anxiety in humans and anxiety-like behavior in animals). We also investigated the neural correlates of yohimbine-induced reinstatement of palatable food seeking behavior by measuring c-Fos expression in the dorsal medial prefrontal cortex (dmPFC) and lateral hypothalamus (LH), with a focus on orexin-A-expressing neurons. Our findings demonstrate that pellet-priming robustly reinstates palatable food seeking behavior in mice, while yohimbine is less effective. Sex differences were minimal. Yohimbine-induced reinstatement was associated with a trend toward increased levels of c-Fos expression in the dmPFC and orexin-A-expressing neurons in the LH relative to saline controls. These results support the use of mice for modeling relapse to palatable food seeking and highlight the dmPFC and LH orexin system as potential targets for future research on stress-induced diet relapse.

Keywords

Diet Relapse, Stress, Medial Prefrontal Cortex, Lateral Hypothalamus, Orexin

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