Recurrent autonomic dysreflexia exacerbates vascular dysfunction after spinal cord injury

BACKGROUND CONTEXT: Individuals with high spinal cord injury (SCI) are prone to significant fluctuation in blood pressure with episodes of very high and low blood pressure during autonomic dysreflexia (AD) and orthostatic hypotension. respectively. We do not know how such blood pressure lability affects the vasculature. PURPOSE: We used a well-characterized animal model of AD to determine whether increasing the frequency of AD during recovery from SCI would exacerbate injury-induced dysfunction in resistance vessels. STUDY DESIGN/SETTING: Experimental animal study. International Collaboration On Repair Discoveries (ICORD), University of British Columbia, Canada. METHODS: Complete transection of the T3 spinal cord was performed in male Wistar rats. For 14 days after injury, AD was induced via colorectal distension (CRD; 30 minutes per day) in the experimental group (SCI-CRD). One month after SCI, baseline cardiovascular parameters and severity of CRD-induced AD were assessed in SCI-CRD animals and SCI-only controls. Mesenteric arteries were harvested for in vitro myography to characterize vasoactive responses to phenylephrine (PE) and acetylcholine (ACh). RESULTS: Mesenteric arteries from SCI-CRD animals exhibited larger maximal responses to PE than arteries from SCI-only controls. Hyperresponsiveness to PE was not a product of endothelial dysfunction because mesenteric arteries from both groups had similar vasodilator responses to ACh. Both SCI-only controls and SCI-CRD animals exhibited CRD-evoked AD 1 month after SCI; however, CRD-induced hypertension was less pronounced in animals that were previously exposed to CRD. CONCLUSIONS: Injury-induced changes within the vasculature may contribute to the development of AD after SCI. Here, we provide evidence that AD itself has significant and long-lasting effects on vascular function. This finding has implications for the medical management of AD and provides an impetus for maintaining stable blood pressure. (C) 2010 Elsevier Inc. All rights reserved.