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Chronic Paraplegia is Associated with Abnormal Cardiac Autonomic Balance and Changes in Baroreflex Control in Normotensive Rats
Author(s) -
Haverland Nicole A,
Rodenbaugh David W
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.609.2
Subject(s) - medicine , baroreflex , autonomic dysreflexia , blood pressure , spinal cord injury , heart rate , balance (ability) , angiotensin ii , cardiac function curve , paraplegia , autonomic nervous system , cardiology , spinal cord , endocrinology , anesthesia , heart failure , physical therapy , psychiatry
There are 250,000 to 400,000 individuals with spinal cord injury (SCI) in the United States and 11,000 new injuries are reported every year. Improvements in acute care and rehabilitation have increased the life expectancy of individuals with SCI to that of able‐bodied individuals. Significant cardiovascular disorders are associated with SCI including, episodic bouts of hypertension known as autonomic dysreflexia, and altered blood pressure related cardiovascular disease (BP‐CVD) risk factors such as elevated heart rate. It has previously been reported that spontaneously hypertensive rats had significantly elevated cardiac sympathetic tone two weeks after spinal cord transaction. However, it has not been demonstrated if the balance between cardiac parasympathetic and cardiac sympathetic tone, defined as cardiac autonomic balance (CAB) is altered following SCI in normotensive rats monitored by radiotelemetry. It is unclear whether changes in CAB are due to alterations in baroreflex (BR) control of arterial blood pressure and/or elevations in circulating angiotensin II (Ang‐ II) levels. We predict that CAB will favor enhanced cardiac sympathetic activity and reduced parasympathetic activity. In addition, chronic paraplegic rats will have significant elevations in Ang‐ II as measured by ELISA and a shift in spontaneous BR function in order to compensate for the loss of supra‐spinal control of total peripheral resistance below the injury. CAB was increased 137% 5 weeks post‐SCI relative to intact rats. The increase was due to a complete parasympathetic withdrawal and increased cardiac sympathetic tone. These results suggest SCI significantly alters CAB in a manner that would increase CVD‐risk factors.