Electronic Theses and Dissertations

Date of Award


Document Type


Degree Name

Ph.D. in Psychology



First Advisor

Kenneth J. Sufka

Second Advisor

Michael Allen

Third Advisor

Nicole Ashpole

Relational Format



An increasing body of literature suggests a Major Depressive Disorder subpopulation, Treatment Resistant Depression (TRD), is associated with an increased immune response. More than a decade of research has identified and begun to validate a novel animal model of TRD. This study sought to determine whether TNF-α levels would be altered due to isolation stress and differentiated between stress-vulnerable and -resilient strains. Black Australorp and Production Red chicks were placed into isolation for varying times during which Distress Vocalization (dVoc) rates were calculated and transformed into entry into behavioral despair percent thresholds. Blood levels of TNF- α were quantified via ELISA either directly from the home cage and served as non-isolated controls or following isolation stress. Black Australorps entered into behavioral despair significantly more quickly than Production Reds. Non-isolated controls show no TNF-α level differences. Production Reds displayed an increase in TNF-α levels with a peak at 60 minutes in the isolation test period. Black Australorps displayed a low TNF-α response that remained stable across the isolation test period. These findings identify a blunted TNF-α response in stress-vulnerable Black Australorps that is influenced by a gene x environment interaction. These findings demonstrate the model may be useful for identifying novel cytokine targets for TRD.


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