Date of Graduation

Spring 2019

Degree

Master of Science in Biology

Department

Biology

Committee Chair

Paul Durham

Keywords

temporomandibular joint disorder, trigeminal nerve, peripheral sensitization, central sensitization, risk factors, inflammatory mediators

Subject Categories

Animal Experimentation and Research | Cell Biology | Molecular and Cellular Neuroscience

Abstract

Results from the OPPERA study provided evidence that risk factors such as neck muscle tension, prolonged jaw opening, and female gender increase the likelihood of developing temporomandibular joint disorders (TMJD), which are prevalent, debilitating orofacial pain conditions. Peripheral and central sensitization, which mediate a lowering of the stimulus required for pain signaling, are implicated in the underlying pathology of chronic TMJD. The goal of my study was to investigate cellular changes in the expression of proteins associated with the development of central sensitization. Female Sprague-Dawley rats were injected with complete Freund’s adjuvant in the upper trapezius muscles to promote trigeminal sensitization. After 8 days, animals were subjected to near maximal jaw opening for 20 minutes, and spinal cord tissues were collected at several time points until day 28 post jaw opening. Changes in proteins associated with neuronal and glial cell activation were investigated in the medullary dorsal horn using immunohistochemistry. Somewhat surprisingly, consistently increased protein expression was not observed in second-order nociceptive neurons, astrocytes, or microglia in the dorsal horn. Thus, my results are suggestive that this novel model for inducing chronic TMJD pathology is mechanistically different from other reported inflammatory-induced TMJD models. Based on my results, I propose that this model that involves pain signaling in response to prolonged jaw opening in sensitized animals involves dysfunction of descending inhibitory signaling and likely involves changes in the expression of cytokines and miRNAs.

Copyright

© Jessica R. Cox

Open Access

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