Temporomandibular muscle/joint disorders (TMJD) include a family of painful conditions that involve the temporomandibular joint (TMJ) and muscles of mastication. Risk factors for chronic TMJD pain include female sex hormone status and stress related mood disorders. Serotonin is a common monoamine neurotransmitter in the brain and has been linked to neural pathways involved in both pain sensation and mood disorders. Serotonin receptors are found in brain areas known to receive inputs from sensory nerves that innervate the TMJ region. The main hypothesis was: does estrogen status and/or chronic stress alter the expression of serotonin receptors in regions of the brain known to be important for TMJ pain processing? Ovariectomized (OvX) female rats were treated with either high or low levels of estradiol then subjected to a repeated forced swim test (FST). Brainstems were removed and processed for serotonin receptor levels by quantitative Polymerase Chain Reaction (qPCR) and immunoblotting. Five types of serotonin receptors were studied: 5HT-1A, 5HT-2A, 5HT-3A, 5HT-4, and 5HT-7. While the qPCR results showed that there is not a statistically significant difference between high and low estrogen groups, there is a statistically significant difference between FST and control groups for receptor 5HT-1A. This finding confirms that there is a down regulation of serotonin receptors when the rats undergo a FST. The results from the Western blot were not conclusive.
Faculty advisers: David Bereiter and Randy Thompson.
This research was supported by the Undergraduate Research Opportunities Program (UROP).
Hillstrom, Ashley; Thompson, Randy; Bereiter, David.
The Effects of Estrogen and Stress on the Expression of Serotonin Receptors in the Rat Brainstem.
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