Ph.D. (Doctor of Philosophy)
Department of Psychology
Motivational dysfunction is present in a variety of disorders, including major depressive disorder, schizophrenia, and Parkinsonism and can negatively impact social functioning, employment, and treatment response. Interestingly, outside stressors and stress hormones have been shown to contribute to depressive episodes in humans and depressive-like behaviors in rodents, including reducing motivated behaviors. Effort-related decision making procedures have been utilized in both humans and animals in order to examine motivational dysfunction, as it offers a subject a choice between high effort/reward and low effort/reward options, but little research has examined the effects of stress on effort-related decision making behaviors. Moreover, almost all the research that has considered motivational dysfunction in effort-based tasks has been conducted in males, despite prior research consistently showing sex differences in the prevalence of depression and depressive-like behaviors in humans. Therefore, the current study investigated the impact of acute stressors on effort-related decision making procedures in male and female rats (Experiment 1), assessed the role of the stress peptide hormone CRF on task performance in male and female rats (Experiment 2), and determined whether acute stress influenced dopamine in the nucleus accumbens (Experiment 3). Animals were trained in an FR5 task where they could lever press for a sucrose reward or consume freely available standard lab chow. Then, animals were exposed to various acute stressors. In Experiment 1, it was found that 60 minutes of restraint stress or an injection of yohimbine reduced performance in the task, as measured by total number of lever pressing, and that the sexes significantly differed in lever pressing performance with stress. In Experiment 2, while 60 minutes of restraint stress reduced lever pressing performance similar to Experiment 1, administration of a CRF antagonist did not attenuate this response nor did exogenous CRF affect responding. Finally, in Experiment 3, it was found that there were no differences in dopamine content in the nucleus accumbens nor were there sex differences when comparing baseline to various stress conditions. Collectively, these findings contribute to our understanding of the influence of stress and sex differences on motivational dysfunction to provide better options for effort-related behaviors in populations impacted by these symptoms.
Errante, Emily Laine, "Investigating the influence of Stress on Motivational Dysfunction in Male and Female Rodents" (2022). Graduate Research Theses & Dissertations. 7014.
Northern Illinois University
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