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Date of Award

Summer 8-1-2024

Document Type

Applied Project

Degree Name

Master of Science in Research Psychology (MS)

Department

Psychology

Supervisor

Dr. Philip Baker

Second Reader

Dr. Jenny Lee Vaydich

Third Reader

Dr. Jessica Fossum

Keywords

High Fat, Neuroinflammation, Social Isolation, Rodent, Behavior, Pain

Abstract

Prior research has established a role for both social isolation and exposure to high fat Western diets in altering a range of behaviors from reduced memory performance to increased depression-like behaviors. The present study scrutinizes the interplay among these variables during the peri-adolescent developmental phase, utilizing Long-Evans rats as the experimental model. Our overarching hypothesis is that rats exposed to either social isolation, a high-fat diet, or both will result in heightened pain sensitivity, diminished cognitive flexibility, and increased neuroinflammatory responses within brain regions implicated in sociability, cognition, memory, and pain processing. Behavioral flexibility will be assessed using a maze-based strategy switching task where animals are required to switch between allocentric and egocentric strategies. Pain sensitivity evaluations were conducted at three time points throughout the interventions using the manual Von Frey test. Subsequently, neuroinflammatory markers were assayed upon study completion to elucidate the presence of neuroinflammatory responses within select brain regions such as the somatosensory cortex, nucleus accumbens, prelimbic cortex, and hippocampus. A General linear model analysis was employed to detect disparities in pain sensitivity or behavioral flexibility among, diet, and housing conditions. Preliminary results indicate that no statistically significant differences in pain sensitivity were observed across experimental groups when controlling for weight. However, upon omitting weight as a covariate, the sex condition emerged as significantly different in terms of pain tolerance, with males exhibiting greater tolerance compared to females (b = -78.12, p < 0.03, 95% CI [-142.16, -14.08]). Additionally, housing conditions exerted a notable difference in pain tolerance, with group-housed rats displaying higher pain tolerance compared to their relative group of socially isolated rats (b = 78.11, p < 0.04, 95% CI [14.07, -142.16]). Additional analysis will determine whether differences in behavioral flexibility are also present and further, whether interactions between levels of astrocyte, or microglia activation mediate observed effects on pain and behavioral flexibility. Overall, initial results indicate that social isolation through adolescence can increase pain sensitivity in adulthood with females being especially susceptible.

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