Author ORCID Identifier

https://orcid.org/0000-0001-7737-1182

Date Available

4-29-2022

Year of Publication

2022

Degree Name

Master of Science in Medical Sciences (MSMS)

Document Type

Master's Thesis

College

Medicine

Department/School/Program

Neuroscience

First Advisor

Dr. Warren Alilain

Second Advisor

Dr. John Gensel

Abstract

Spinal cord injury, specifically in the cervical C3-C4 region of the cervical spine, contributes to impaired breathing and a diminished quality of life. Therefore it is important to find effective and safe therapeutics to restore breathing function. Indeed, there are a myriad of research being performed in addition to valuable collaboration amongst different institutions. As such, inspired by a previous experiment, we decided to test our hypothesis that an enriching environment consisting of different hypoxic environments - sustained and intermittent hypoxia alongside normoxia - would result in neurite outgrowth. Moreover, we hypothesized that sustained hypoxia would result in the greatest neurite outgrowth, followed by intermittent hypoxia. Lastly, we predicted that normoxia would result in the smallest amount of neurite outgrowth. We tested this hypothesis first in-vivo by placing female, retired breeder rats (n=3) in sustained or intermittent hypoxia or normoxia conditions for a period of 2 hours and 32 minutes. This was followed by dorsal root ganglion (DRG) culturing, plating, and fixing. Notably, because the premise of this experiment is a hybrid of both an in-vivo and in-vitro (specifically an ex-plant) we cannot, with accuracy, state that the growths are of axonal in nature. As such, we will refer them to as neurite. We used NeuronJ to manually trace and measure neurite outgrowth. In addition, we also utilized the Sholl analysis to better understand neurite arborization and their location in relation to the soma. We conclude that, interestingly, normoxia resulted in the greatest neurite outgrowth, followed by intermittent hypoxia and lastly by sustained hypoxia. As such, this experiment augments others experiments that show the promising therapeutic effects of intermittent hypoxia in restoring breathing function whether it is through enhancement of the crossed phrenic pathway or increased serotonergic receptor activation.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2022.141

Funding Information

This study was funded by the National Institute of Neurological Disorders and Stroke. The sponsor ID number for this grant is R501NS101105. The title of the grant is "Promoting and Understanding Recovery of Breathing After Chronic Spinal Cord Injury," with the timeframe for use between 2021-2022.

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