The Bullied Prairie Vole: Modeling Depression And Anxiety Through Social Defeat Stress

Stress-induced illnesses, such as major depression and anxiety, are significant global causes of disability. This highlights the need for reliable animal models that accurately mimic social stress-induced maladaptations, thus, allowing the experimental study of the etiology of such disorders. Prairie voles (Microtus ochrogaster), known for their human-like bi-parental behavior and monogamous partner preferences, are a relevant model for the study of stress-induced psychopathologies. For this reason, in this dissertation, I examined whether exposing voles to the social defeat stress (SDS) paradigm, an experimental approach that captures bullying behavior, would result in both depression and anxiety-related profiles. To do this, experimental voles were exposed to 10-minute agonistic interactions with a paired male aggressor over 10 consecutive days, as it is conventionally done in laboratory mice. Control animals were housed under similar conditions but did not experience stress. To evaluate the effects of SDS on depression-related behavior, I adopted (1) the social interaction test, (2) sucrose preference, and (3) Morris water maze tests, which are validated approaches to assess depressive-relevant phenotypes (i.e., social withdrawal, anhedonia, and spatial memory impairment, respectively). Additionally, I evaluated responses to open-space exploratory behavior on the (4) light/dark box and (5) elevated plus-maze tests, since they are commonly adopted to study anxiety-related behavior across rodent species. I found that SDS decreased body weight, sociability, sucrose preference (anhedonia), exploratory behavior, and impaired spatial memory performance. No changes in general locomotor activity were noted between the experimental groups. Collectively, the findings of this dissertation support the notion that the SDS model, in male prairie voles, is a valuable tool for studying stress-induced phenotypes that resemble human-like depression and anxiety-relevant profiles.