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Access Type
WSU Access
Date of Award
January 2024
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Psychiatry and Behavioral Neurosciences
First Advisor
Alana C. Conti
Second Advisor
Shane A. Perrine
Abstract
Mental health disorders, such as post-traumatic stress disorder (PTSD), are complex, leaving challenges for the development of effective interventions. Increasing our detailed understanding of these disorders, by studying the micro-neurocircuitry behind them, can help provide tailored solutions corresponding to the complexity of the individual’s symptoms. This micro-neurocircuitry can be investigated by studying small groups of highly-active neurons, collectively known as neuronal ensembles, that are accountable for unique behavioral responses, e.g. fear learning, in PTSD. Behavioral studies examining neuronal ensembles have thus far been largely ex vivo, using immediate early genes associated with neuronal activity (e.g. Fos). In vivo imaging methods are currently limited (very invasive or low resolution), and generally measure indirect neuronal activity, such as the blood oxygen dependent response. To address this knowledge gap, we developed a new high-resolution imaging approach to detect and quantify fear-related neuronal activity in vivo, with the goal of discovering more detailed roles of the neuronal ensembles that mediate fear learning.Specifically, we used photoacoustic (PA) imaging to map activated neurons in vivo in a Fos-LacZ transgenic rat model. Fusion of Fos, which is induced by neuronal activity, with the lacZ gene product β-galactosidase gives active (Fos+) cells the ability to cleave pro-chromogenic substrates, such as X-Gal, enzymatically, into PA-active dyes. My phantom and ex vivo pilot studies in rat brains demonstrate high-contrast PA images using these dyes and image reconstructions with a very high signal-to-noise ratio. We hypothesized that during fear acquisition, unique neuronal ensembles will be activated and detectable in the medial prefrontal cortex (a region tightly associated with fear behavior) using a novel Fos-LacZ PA imaging system, providing a means to track longitudinal changes in these ensembles in vivo. To test this hypothesis, we used male and female Fos-LacZ transgenic rats administered X-Gal upon exposure to footshock (fear). This technique was first developed (Chapter 2) and then tested in vivo and validated with traditional methods for immunohistochemical detection of c-Fos and β-Gal in brain slices ex vivo (Chapter 3). This project provided deeper insight into the role of fear-related neuronal ensembles and a new wide field-of-view, low cost, high-resolution methodological approach to measure c-Fos expression (representative of neuronal ensembles) in vivo. This will be broadly useful for behavioral research, not only in PTSD, but also in a variety of psychiatric models by allowing us to better define mechanisms behind complex mental health disorders.
Recommended Citation
Matchynski, James Ivan, "Development And Implementation Of A Novel Method To Quantify Fos-Related Neuronal Activity In Vivo Using High-Resolution Photoacoustic Imaging" (2024). Wayne State University Dissertations. 3738.
https://digitalcommons.wayne.edu/oa_dissertations/3738