Date of Award


Document Type

Open Access Honors Thesis

Degree Name

Bachelor of Science (BS)




Tiffany Donaldson


Rajini Srikanth

Subject Categories

Biological Psychology | Biology


Rats, like humans, show personality traits: they are born with different anxiety levels (i.e., high (HAn) or low anxiety (LAn) levels). In this study, we investigated (1) if treatment with valproic acid (VPA) can lower anxiety level in trait anxiety rats and (2) how VPA may interact with environment (e.g., enriched (EE), standard (SE) and isolated environments (IE)). VPA is a deacetylase inhibitor that increases Histone 3 acetylation, a known epigenetic mechanism that interacts with stress response proteins, and treats epilepsy and mood disorders. Since rats reared in IE exhibit heightened anxiety levels as compared to those in EE, we suspected that there would be an additive effect of VPA treatment and EE – that this combined treatment would lower the anxiety levels of HAn rats. In order to verify that VPA improved performance on anxiety tests by interacting with the stress response system, Long Evan Rats were perfused with 4% paraformaldehyde for brain tissue analysis using immunohistochemistry to measure corticotropin releasing factor (CRF), a protein implicated in stress. We found that Long Evan rats housed in EE showed less anxiety-like behavior on the EPM compared to other housing settings, and surprising, this was reversed with VPA. VPA did lower anxiety-like behavior in IE reared animals. There was a decrease in the CRF levels in LANEE, and an increase CRF in the HANEE housed animals, suggesting no additive effect of combining VPA and EE treatment for anxiety-like behavior, but a benefit for reversing anxiety due to isolation rearing.