Honors Theses

Date of Award

Spring 5-9-2020

Document Type

Undergraduate Thesis



First Advisor

Alberto Del Arco

Relational Format



Repeated exposure to stress is known to have a myriad of effects on the brain, contributing to the development of psychiatric disorders, such as anxiety, depression, and drug addiction. For example, rats undergoing repeated social stress develop increased cocaine self-administration. These effects of stress are not well-understood and are related to changes in the brain reward system. This study investigated the effects of repeated social stress on reward-seeking behavior via the acquisition and extinction of a discriminative stimulus (DS) task and on anxiety-like behavior in the elevated plus maze (EPM). Male rats underwent intermittent social defeat (4 sessions in 10 days) using the resident-intruder paradigm. Animals were tested in the DS task in between stress sessions for Experiment 1 and one month after the last session for Experiment 2. The EPM was conducted 3 days after the last stress session. In the DS task, stress did not change the acquisition of reward-seeking behavior in the days in between stress sessions, and Stress and Control groups responded similarly to reward-seeking cues. However, stress did affect reward-seeking behavior in the long term, as the Stress group averaged less responses during the first extinction trial one month after stress, indicating a faster extinction response. In addition, the Stress group spent more time in the open arms of the EPM than the Control group, exhibiting a higher tendency towards risk-taking behavior. These results suggest that social stress does not produce effects in the reward system in the short term, but does produce changes in the long term.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.