Document Detail


Autonomic blockade and cardiovascular responses to static exercise in partially curarized man.
MedLine Citation:
PMID:  2600859     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
1. The cardiovascular responses, heart rate and mean arterial pressure, were followed in seventeen human subjects who performed static handgrip contractions for 2 min at the same absolute force (15% of the initial maximal voluntary contraction strength) before and during partial curarization. In control contractions the rate of perceived exertion was 10 exertion units, 16 units in contractions with tubocurarine which could be maintained and 20 units in contractions that could not be maintained. Control contractions increased mean arterial pressure by 6 mmHg from 89 mmHg while heart rate was unchanged from the resting value of 68 beats min-1. With tubocurarine, larger increases in mean arterial pressure of 11 mmHg and for heart rate of 8 beats min-1 were obtained during maintained contractions, and 15 mmHg and 16 beats min-1, respectively, during non-maintained contractions. 2. Atropine increased resting heart rate and blood pressure with tubocurarine to 107 beats min-1 and 98 mmHg, respectively, in seven subjects. The blood pressure response to exercise with tubocurarine was unaffected by atropine, but the heart rate increase was reduced from 15 to 4 beats min-1. 3. Propranolol reduced resting heart rate with tubocurarine to 56 beats min-1 with no effect on blood pressure in seven subjects. The cardiovascular responses to exercise with tubocurarine were unaffected by propranolol. In contrast, phentolamine reduced resting blood pressure with tubocurarine to 80 mmHg without affecting heart rate in seven subjects. Exercise responses with tubocurarine were unaffected by phentolamine. Combinations of atropine and propranolol in fourteen subjects or atropine and phentolamine in five subjects showed similar results during exercise with tubocurarine as with the sole use of the agents used to block autonomic receptors. 4. The results suggest that when partial curarization induces a disproportion between the signal from central command and that from exercising muscles, the larger signal arising from central command determines the magnitude of the cardiovascular responses. The centrally generated heart rate response is in part caused by vagal withdrawal. However, the blood pressure response cannot be attenuated by the sole use of alpha- or beta-receptor adrenergic blockade or combinations of these with atropine. This suggests that there may be greater redundancy in the autonomic control of blood pressure than in the vagal control of heart rate associated with central command during static exercise in man.
Authors:
J H Mitchell; D R Reeves; H B Rogers; N H Secher; R G Victor
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of physiology     Volume:  413     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1989 Jun 
Date Detail:
Created Date:  1990-01-29     Completed Date:  1990-01-29     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  433-45     Citation Subset:  IM    
Affiliation:
Department of Anaesthesia, Rigshospitalet, University of Copenhagen, Denmark.
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MeSH Terms
Descriptor/Qualifier:
Adult
Atropine / pharmacology
Autonomic Nervous System / drug effects*
Blood Pressure / drug effects*
Exercise / physiology*
Female
Heart Rate / drug effects*
Humans
Male
Middle Aged
Muscle Contraction / drug effects*
Phentolamine / pharmacology
Propranolol / pharmacology
Tubocurarine / pharmacology*
Chemical
Reg. No./Substance:
50-60-2/Phentolamine; 51-55-8/Atropine; 525-66-6/Propranolol; 57-95-4/Tubocurarine
Comments/Corrections

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