Christopher R West1, Mark A Crawford1, Ismail Laher1, Matt S Ramer1, Andrei V Krassioukov2. 1. University of British Columbia, Vancouver, British Columbia, Canada. 2. University of British Columbia, Vancouver, British Columbia, Canada GF Strong Rehabilitation Centre, Vancouver Health Authority, British Columbia, Canada krassioukov@icord.org.
Abstract
BACKGROUND: Spinal cord injury (SCI) induces alterations in cardio-autonomic control of which autonomic dysreflexia (AD), a condition characterized by life-threatening hypertension, is arguably the most insidious. Passive hind-limb cycling represents a low-cost therapeutic intervention with demonstrable cardiovascular, sensory, and motor benefits. OBJECTIVE: To investigate the effect of passive hind-limb cycling on AD in rodents with T3 SCI. METHODS: Forty-five male Wistar rats were evenly assigned to either uninjured control (CON), SCI, or SCI plus hind-limb cycling exercise (SCI-EX). At the end of the experimental period (day 32), rats were randomly assigned to stream 1 (n = 24) or stream 2 (n = 21). Stream 1 rats were assessed for AD severity (pressor response to colorectal distension) and were then perfused for tissue dissection and immunohistochemistry. Stream 2 rats underwent excision of the superior mesenteric artery for in vitro myography assessments. RESULTS: From 2 weeks post-SCI onwards, SCI-EX rats exhibited a significant reduction in the pressor response to colorectal distension versus SCI (P< .001). Reduced AD severity in SCI-EX rats was accompanied by a prevention of the SCI-induced increase in density of CGRP(+)afferents in the dorsal horn (P= .001). Conversely, both SCI and SCI-EX rats exhibited a similar degree of mesenteric endothelial dysfunction and α-adrenoceptor hypersensitivity versus CON. CONCLUSION: Passive hind-limb cycling reduces the severity of AD in SCI, and is correlated with changes in primary afferent morphology, but has limited effects on the peripheral vasculature.
BACKGROUND:Spinal cord injury (SCI) induces alterations in cardio-autonomic control of which autonomic dysreflexia (AD), a condition characterized by life-threatening hypertension, is arguably the most insidious. Passive hind-limb cycling represents a low-cost therapeutic intervention with demonstrable cardiovascular, sensory, and motor benefits. OBJECTIVE: To investigate the effect of passive hind-limb cycling on AD in rodents with T3 SCI. METHODS: Forty-five male Wistar rats were evenly assigned to either uninjured control (CON), SCI, or SCI plus hind-limb cycling exercise (SCI-EX). At the end of the experimental period (day 32), rats were randomly assigned to stream 1 (n = 24) or stream 2 (n = 21). Stream 1 rats were assessed for AD severity (pressor response to colorectal distension) and were then perfused for tissue dissection and immunohistochemistry. Stream 2 rats underwent excision of the superior mesenteric artery for in vitro myography assessments. RESULTS: From 2 weeks post-SCI onwards, SCI-EX rats exhibited a significant reduction in the pressor response to colorectal distension versus SCI (P< .001). Reduced AD severity in SCI-EX rats was accompanied by a prevention of the SCI-induced increase in density of CGRP(+)afferents in the dorsal horn (P= .001). Conversely, both SCI and SCI-EX rats exhibited a similar degree of mesenteric endothelial dysfunction and α-adrenoceptor hypersensitivity versus CON. CONCLUSION: Passive hind-limb cycling reduces the severity of AD in SCI, and is correlated with changes in primary afferent morphology, but has limited effects on the peripheral vasculature.
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