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Vascular changes in spinal cord injured animals with repetitive episodes of autonomic dysreflexia

University of British Columbia

Spinal cord injury (SCI) is a devastating condition that not only leads to paralysis, but also causes dramatic changes in cardiovascular function. Individuals with cervical or high thoracic SCI commonly suffer from a life threatening condition known as autonomic dysreflexia (AD). AD is characterized by episodic hypertension─ an exaggerated sympathetic response triggered by irritating stimulus below the level of injury e.g. distended bladder. As a lifespan of SCI patients increases, cardiovascular-related illnesses become more prevalent. Recent studies suggest marked vascular dysfunction within the critical splanchnic vascular bed. Mesenteric arteries from rats with chronic high-thoracic SCI are hypersensitive to the α₁-adrenoceptor agonist PE. The hypersensitivity of splanchnic vascular bed in response to PE develops over time after SCI and may contribute to the development of AD. In this dissertation, I examined the morphological changes in peripheral vasculature following repetitive episodes of AD in animals with high SCI. I hypothesized that recurrent episodes of AD will trigger an inward eutrophic remodeling in peripheral resistance arteries of SCI rats. In this study, male Wistar rats with complete spinal cord transection at third (T3) thoracic segment were utilized. At 2 weeks after the injury, AD was induced in rats with T3 SCI using CRD. 4 weeks following injury superior mesenteric (SMA) arteries and primary branches (PMA) were collected from T3 SCI-only, T3+CRD and control uninjured rats. Morphological characteristics such as media thickness, lumen diameter, wall-to-lumen ratio and wall cross sectional area (CSA) of the arteries were evaluated. Results suggest that AD induced through CRD lead to structural remodeling of PMAs, but no changes were observed in SMAs of CRD group. Media thickness, wall-to-lumen ratio significantly increased in PMAs of CRD group; lumen diameter and CSA of PMAs in CRD did not change when compared to T3 SCI-only and uninjured groups. The data support eutrophic (no change in CSA) remodeling of PMAs in CRD group, but failed to show a reduction in lumen diameter (inward changes) of these arteries. The findings of the study highlight the underlying effect of AD on structural remodeling of vasculature following an injury.

Text

2012-10-24

Attribution-NonCommercial-ShareAlike 3.0 Unported

http://hdl.handle.net/2429/43531

Experimental Medicine

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-sa/3.0/