c-Fos Distribution in the Thoracic Spinal Cord After Cervical Spinal Cord Stimulation and Injury
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PI name: Dr. Erica Dale
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Graduate student mentor: Alyssa Mickle
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Institution and department: Physiology and Aging
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Amount of time you have been affiliated with the project: November 2023 - present
Introduction
The Dale lab has recently shown that CL-ES restores some ipsilesional diaphragm EMG activity in C2 hemisected (C2-HS) rats. In these rats we further saw that stimulation redistributed localization of c-Fos, an immediate early gene which can be used as a marker of increased neuronal activity, at C4. Further, we have seen in a preliminary study of uninjured rats that CL-ES increases inspiratory pressure generation even with limited increases in diaphragm EMG output which may indicate accessory muscle activation. Epidural stimulation on the ventral surface of the thoracic cord activates both intercostals and the diaphragm through spinal reflex pathways; however, it is currently unknown if stimulation targeting the diaphragm on the dorsal surface of C4 can activate similar pathways. As spinal pathways which coordinate diaphragm and intercostal muscle activity offer a neural substrate by which stimulation at C4 could lead to intercostal accessory muscle activation, I have begun investigating c-Fos expression at the thoracic level after CL-ES.
Initial Study
(Spring 2024)
My initial study from spring 2024 indicates shifts in c-Fos localization in the thoracic spinal cord. We found a high percentage of non-neuronal c-Fos positivity in the white matter of sham animals, suggesting that electrical stimulation reduces neuronal firing.
Future directions include identifying the c-Fos positive cells in the white matter that are downregulated with stimulation.
Current Study
My current study aims to further investigate whether stimulation induces changes in c-Fos expression not only at C4 but also in the intercostal motor pool. Additionally, I plan to explore why the c-Fos positive cells in the white matter were downregulated with stimulation in my initial spring 2024 study.
My first aim is to determine if there are increases in the amount, location or type of cell producing c-Fos in the thoracic spinal cord in response to closed-loop cervical spinal cord stimulation after C2-HS.
My second aim is to determine if the neurotrophic factor BDNF and its receptor TrkB are expressed in the thoracic spinal cord in response to closed-loop cervical spinal cord stimulation after C2-HS.
Hypothesis: c-Fos, particularly within neurons in the ventral horn, will be upregulated in response to CL-ES after C2-HS. BDNF and TrkB will be upregulated, particularly in c-Fos positive cells.
Summer Updates
(as of August 30th, 2024)
This past summer, I primarily focused on sectioning new tissue from a new group of urethane-anesthetized rats that underwent hour-long bouts of stimulation of varying current intensities.
I also learned how to perform a perfusion and place an arterial catheter during surgery. Additionally, I completed one round of immunohistochemistry (IHC).
This fall, I plan to continue sectioning tissue and conduct further research on specific targets that might cause the downregulation of c-Fos in the white matter.
Photo of rat blood pressure after placing an arterial catheter
Photo of learning how to place an arterial catheter during surgery
Photo of learning how to perform a perfusion