Document Detail

Human autonomic rhythms: vagal cardiac mechanisms in tetraplegic subjects.
MedLine Citation:
PMID:  8014908     Owner:  NLM     Status:  MEDLINE    
1. We studied eight young men (age range: 20-37 years) with chronic, clinically complete high cervical spinal cord injuries and ten age-matched healthy men to determine how interruption of connections between the central nervous system and spinal sympathetic motoneurones affects autonomic cardiovascular control. 2. Baseline diastolic pressures and R-R intervals (heart periods) were similar in the two groups. Slopes of R-R interval responses to brief neck pressure changes were significantly lower in tetraplegic than in healthy subjects, but slopes of R-R interval responses to steady-state arterial pressure reductions and increases were comparable. Plasma noradrenaline levels did not change significantly during steady-state arterial pressure reductions in tetraplegic patients, but rose sharply in healthy subjects. The range of arterial pressure and R-R interval responses to vasoactive drugs (nitroprusside and phenylephrine) was significantly greater in tetraplegic than healthy subjects. 3. Resting R-R interval spectral power at respiratory and low frequencies was similar in the two groups. During infusions of vasoactive drugs, low-frequency R-R interval spectral power was directly proportional to arterial pressure in tetraplegic patients, but was unrelated to arterial pressure in healthy subjects. Vagolytic doses of atropine nearly abolished both low- and respiratory-frequency R-R interval spectral power in both groups. 4. Our conclusions are as follows. First, since tetraplegic patients have significant levels of low-frequency arterial pressure and R-R interval spectral power, human Mayer arterial pressure waves may result from mechanisms that do not involve stimulation of spinal sympathetic motoneurones by brainstem neurones. Second, since in tetraplegic patients, low-frequency R-R interval spectral power is proportional to arterial pressure, it is likely to be mediated by a baroreflex mechanism. Third, since low-frequency R-R interval rhythms were nearly abolished by atropine in both tetraplegic and healthy subjects, these rhythms reflect in an important way rhythmic firing of vagal cardiac motoneurones.
J Koh; T E Brown; L A Beightol; C Y Ha; D L Eckberg
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of physiology     Volume:  474     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1994 Feb 
Date Detail:
Created Date:  1994-07-22     Completed Date:  1994-07-22     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  483-95     Citation Subset:  IM; S    
Department of Medicine, Hunter Holmes McGuire Department of Veterans Affairs Medical Center, Richmond, VA.
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MeSH Terms
Atropine / pharmacology
Autonomic Nervous System / physiopathology*
Blood Pressure
Carotid Arteries / innervation,  physiology
Catecholamines / blood
Heart / drug effects,  innervation,  physiology*,  physiopathology
Motor Neurons / physiology
Nitroprusside / pharmacology
Phenylephrine / pharmacology
Pressoreceptors / physiology
Quadriplegia / physiopathology*
Spinal Cord Injuries / physiopathology
Vagus Nerve / physiology
Grant Support
Reg. No./Substance:
0/Catecholamines; 15078-28-1/Nitroprusside; 51-55-8/Atropine; 59-42-7/Phenylephrine
D L Eckberg / Med Coll VA, Richmond

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