Year of Publication

2016

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Medicine

Department

Anatomy and Neurobiology

First Advisor

Dr. Gregory Bix

Second Advisor

Dr. Justin Fraser

Abstract

Stroke is the 5th leading cause of death in the U.S. with 130,000 deaths and around 800,000 affected annually. Currently, there is a significant disconnect between basic stroke research and clinical stroke therapeutic needs. Few animal models of stroke target the large vessels that produce cortical deficits seen in the clinical setting. Also, current routes of drug administration, intraperitoneal and intravenous, do not mimic the clinical route of intra-arterial drug administration. To bridge this divide, we have retro-engineered a mouse model of stroke from the current standard of care for emergent large vessel occlusion (ELVO) stroke, endovascular thrombectomy, to include selective intra-arterial pharmacotherapy administration. Using the tandem transient common carotid and middle cerebral artery occlusion (MCAo) model to induce stroke, we threaded micro-angio tubing into the external carotid artery (ECA) towards the bifurcation of the common carotid and internal carotid arteries (CCA/ICA) allowing for the delivery of agents to the site of acute ischemia. Our model was optimized through a flow rate and injection volume study using carbon black ink injected through the intra-arterial model at different flow rates and injection volumes. The purpose of this study was to demonstrate that our injections were arriving at the site of ischemia and to improve injection volumes for future dosing while mitigating systemic side effects by preventing or minimizing systemic distribution. We determined that a flow rate of 2.5 µl/minute and injection volume of 10 µl was optimal. Next, we tested potential neuroprotective compounds nitroglycerin, verapamil, and a combination of verapamil and lubeluzole. Compounds were chosen for drug synergy and to target specific pathways in either an acute or delayed manner. Acute treatments included nitroglycerin and/or verapamil while delayed treatment included lubeluzole. The known mechanism of action for FDA approved nitroglycerin is through vessel dilation that results in increased blood flow to the treated region. A secondary mechanism of nitroglycerin is the production of nitric oxide, which has demonstrated antioxidant and anti-apoptotic effects when processed and released from cells surrounding the blood vessels. Verapamil, a calcium channel blocker, also FDA-approved for cerebral artery vasospasm: is thought to act by blocking the L-type calcium channels on the cell membrane from opening following membrane depolarization after insult. Finally, lubeluzole, also FDA-approved, is proposed to work as an NMDA modulator inhibiting the release of glutamate and nitric oxide synthase and blocking sodium and calcium channels. Through our stroke model we were able to demonstrate that each drug(s) showed a significant decrease in infarct volume and improved functional recovery while simultaneously minimizing potential systemic side effects suggesting that our stroke model may improve the preclinical validation of potential stroke therapies and help bridge the bench to bedside divide in developing new stroke therapies.

Digital Object Identifier (DOI)

https://doi.org/10.13023/ETD.2016.394

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