title: Exercise pressor reflex function following acute hemi-section of the spinal cord in cats.
abstract: Cardiovascular disease is a leading cause of morbidity and mortality in patients post spinal cord injury (SCI). The prescription of exercise as a therapeutic modality for disease prevention in this population is promising. It is logical to suggest that the sooner an exercise program can begin the more benefit the patient will receive from the therapy. However, the time point after injury at which the requisite circulatory responses needed to support exercise are viable remains largely unknown. The skeletal muscle exercise pressor reflex (EPR) significantly contributes to cardiovascular control during exercise in healthy individuals. Experiments in patients with a chronic lateral hemi-section of the spinal cord (Brown-Séquard syndrome) suggest that the EPR, although blunted, is operational when examined months to years post injury. However, whether this critically important reflex remains functional immediately after lateral SCI or, in contrast, experiences a period of reduced capacity due to spinal shock has not been established. This study was designed to assess EPR function after acute lateral transection of the spinal cord. The EPR was selectively activated in seven decerebrate cats via electrically stimulated static contraction of the triceps surae muscles of each hindlimb before and after lateral hemi-section of the T(13)-L(2) region of the spinal cord. Compared to responses prior to injury, increases in mean arterial pressure (MAP) were significantly decreased when contracting the hindlimb either ipsilateral to the lesion (MAP = 17 ± 3 mmHg before and 9 ± 2 mmHg after) or contralateral to the lesion (MAP = 22 ± 5 mmHg before and 12 ± 4 mmHg after). The heart rate (HR) response to stimulation of the EPR was largely unaffected by induction of acute SCI. The findings suggest that the EPR maintains the ability to importantly contribute to cardiovascular regulation during exercise immediately following a Brown-Séquard-like injury.
authors: Department of Physical Therapy, University of Texas Southwestern Medical Center Dallas, TX, USA ; Department of Applied Physiology and Wellness, Southern Methodist University Dallas, TX, USA.
authors: Megan N
authors: MN
authors: Murphy
authors: Ronaldo M
authors: RM
authors: Ichiyama
authors: Gary A
authors: GA
authors: Iwamoto
authors: Jere H
authors: JH
authors: Mitchell
authors: Scott A
authors: SA
authors: Smith
keywords: blood pressure; cardiovascular disease; heart rate; muscle afferents; spinal cord injury
references: Spinal Cord. 2001 Jun;39(6):310-7
references: 11438852
references: Med Sci Sports Exerc. 2005 Aug;37(8):1356-64
references: 16118583
references: Arch Phys Med Rehabil. 2001 Jun;82(6):832-9
references: 11387591
references: Clin Auton Res. 2002 Dec;12(6):457-64
references: 12598950
references: Annu Rev Physiol. 1983;45:229-42
references: 6342515
references: J Appl Physiol (1985). 1985 Aug;59(2):459-67
references: 4030598
references: Sports Med. 2004;34(11):727-51
references: 15456347
references: J Appl Physiol Respir Environ Exerc Physiol. 1983 Jul;55(1 Pt 1):105-12
references: 6309712
references: Spinal Cord. 2008 Oct;46(10):666-72
references: 18392038
references: J Bone Joint Surg Am. 2009 Nov;91(11):2568-76
references: 19884429
references: Tidsskr Nor Laegeforen. 2012 May 15;132(9):1115-20
references: 22614315
references: J Appl Physiol (1985). 2002 Dec;93(6):1966-72
references: 12433934
references: J Appl Physiol (1985). 2003 Aug;95(2):545-54
references: 12716876
references: Spinal Cord. 2011 Jun;49(6):702-14
references: 21339761
references: Exp Physiol. 2006 Jan;91(1):89-102
references: 16282366
references: J Appl Physiol (1985). 2003 Apr;94(4):1437-45
references: 12482762
references: Am J Physiol Heart Circ Physiol. 2005 May;288(5):H2068-76
references: 15604127
references: J Appl Physiol (1985). 2005 Nov;99(5):1891-6
references: 15994238
references: Spinal Cord. 2011 Nov;49(11):1103-27
references: 21647163
references: J Appl Physiol. 1971 Mar;30(3):434-6
references: 5544129
references: Paraplegia. 1991 Jan;29(1):8-16
references: 2023773
references: Arch Phys Med Rehabil. 2006 Apr;87(4):474-81
references: 16571385
references: Spinal Cord. 2008 Nov;46(11):722-6
references: 18414425
references: Am J Phys Med Rehabil. 2007 Feb;86(2):142-52
references: 17251696
references: Am J Physiol Heart Circ Physiol. 2001 May;280(5):H2153-61
references: 11299217
references: Am J Physiol Heart Circ Physiol. 2011 Oct;301(4):H1191-204
references: 21841019
references: Spinal Cord. 2004 Jul;42(7):383-95
references: 15037862
references: J Physiol. 2000 Aug 15;527 Pt 1:193-202
references: 10944182
references: Brain Res. 1984 Jan 30;292(1):160-4
references: 6697204
references: Spinal Cord. 2009 Jan;47(1):36-43
references: 18957962
references: J Physiol. 1972 Oct;226(1):173-90
references: 4263680
references: Med Sci Sports Exerc. 2005 Jul;37(7):1112-8
references: 16015126
references: J Appl Physiol (1985). 2006 Mar;100(3):800-6
references: 16269524