Refining a Post-Stroke Pharmacological and Physical Treatment to Reduce Infarct Volume or Improve Functional Recovery, using Gene Expression Changes in the Peri-Infarct Region to Examine Potential Mechanisms in Male and Female Rats
Adrian Corbett (Advisor), Jeffery Gearhart (Committee Member), Michael Hennessy (Committee Member), David Ladle (Committee Member), Debra Ann Mayes (Committee Member)
Doctor of Philosophy (PhD)
Stroke, a life-threatening medical condition, is the fifth-leading cause of death in the United States with an estimated annual cost of treatments above $70 billion. A combination of innovative approaches was used in our lab to optimize the pre-clinical stroke research design by choosing the most appropriate animal model and methodologies to increase the translational capability of the stroke research. The first study, modeled after ongoing clinical trials using fluoxetine, refined the appropriate timing of fluoxetine and ascorbic acid delivery if a rat was on simvastatin for 7 days pre-stroke and throughout the remainder of the study. Administration of fluoxetine and ascorbic acid at 6-12 hours or 48-54 hours (the time used in clinical trials) after stroke in male 10-12 month old rats resulted in larger infarct volume and indicated a high risk of hemorrhagic transformation, while administration of the same drugs 20-26 hours after stroke dramatically reduced infarct volume and the risk of bleeding in the brain. The ability of the combination therapy (fluoxetine and simvastatin) to improve motor recovery following stroke was estimated in both rehabilitated and non-rehabilitated female 10-12 month rats. The combination of drugs and rehabilitation improved motor function recovery, but ultimately, the same functional recovery was seen with the drugs when there was no rehabilitation, making this treatment potentially useful for stroke patients who cannot undergo rehabilitation. The Forelimb Asymmetry test for the motor function was refined so that it showed greater sensitivity and correlated better with results from the Montoya's staircase grasping test. Finally, the potential mechanisms by which the pharmacological treatment works to aid recovery were investigated, exploring any putative sex-specific pattern of gene expression in the peri-infarct region in male and female rats at post-stroke day 7. A preliminary genetic analysis along with protein-protein interaction prediction reveal a fundamental role of animal sex in the response to drug treatment. The study shows a variation in the influences of the drug on pro- and anti-inflammatory biomarkers of microglia, regulation of neurotrophic factors and synaptic plasticity, with a new possible role of a neuropeptide Orexin and receptors in mediating the functional recovery in male rats.
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