Date Thesis Awarded
Honors Thesis -- Access Restricted On-Campus Only
Bachelors of Science (BS)
The long-lasting effects of the COVID-19 pandemic are just beginning to emerge as the prevalence of mental illnesses such as depression and anxiety has risen drastically over the past few years. While the set of stressors that contribute to this rise are multifaceted, the forced isolation experienced by many during the pandemic necessitates further exploration of its impact on depressive-like behaviors with the goal of enhancing existing or creating novel treatment options. Many studies using rodent models to explore housing effects impose housing-related stressors such as isolation and results suggest that these are sufficient to induce depression-like behavior. In contrast, insufficient research has been conducted with the goal of promoting the beneficial effects of environmental variables, such as enriched housing, on preventing depression associated behavior in response to stressors. The current study sought to explore this issue using the sucrose preference test, a rodent model of consumption measuring preference for sucrose compared to water in which a decrease in sucrose preference is taken to reflect anhedonic behavior. Null preliminary effects of enriched versus isolation housing on sucrose preference were observed and the focus of the current project shifted to examine age-dependent effects of housing on ahedonia measured in the sucrose preference test. In Experiment 1, housing manipulations were initiated in adulthood and in Experiment 2 in adolescence. Sprague-Dawley male and female rats were singly housed in isolation, or in groups of 2-3 per cage with the addition of enhanced bedding, shelter, and toys which rotated every 3 days. Following 4 weeks and 11 weeks total of housing exposure (Experiment 1) or after 4 weeks only (Experiment 2) subjects were tested in the sucrose preference test for 12 hours. Adult exposed rats failed to display any behavioral alteration as a result of housing condition following either 4 or 11 weeks of housing exposure. Adolescent exposed rats singly housed in a nonenriched environment showed a reduction in sucrose preference compared to group housed environmentally enriched counterparts following 4 weeks of housing manipulations. Adolescent animals also displayed increased anxiety measured in the light-enhanced startle paradigm. These data suggest housing effects in rodents are age-dependent and isolation housing of adolescent but not adult rats induce an anhedonic depressive phenotype. Possible sex effects and critical variables in the sucrose preference test are discussed.
McArdle, Hayden, "Isolation Induced Anhedonic Behavior in Adolescent but not Adult Sprague-Dawley Rats" (2023). Undergraduate Honors Theses. William & Mary. Paper 1990.
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