Document Detail

Reduction of intrinsic sinoatrial frequency and norepinephrine response of the exercised rat.
MedLine Citation:
PMID:  902154     Owner:  NLM     Status:  MEDLINE    
Physical training is associated with a reduction of intrinsic sinoatrial activity; the present study examined the role of the parasympathetic nervous system in this reduction. Six groups of rats were studied for 10 weeks: inactive control; treadmill exercised; parasympathetic receptor blockade with atropine; exercise plus atropine; parasympathetic receptor stimulation with carbachol; and exercise plus carbachol. In vivo ISF (cardiac frequency 20 min after injection of propranolol and atropine) was measured at 3-week intervals. At the end of 10 weeks the right atrium was excised, in vitro measurements were made of ISF, and chronotropic dose-response curves to acetylcholine and norepinephrine were established. In vivo, ISF was reduced with time, the greatest reduction being found in the exercise plus atropine group; the treadmill-exercised and the atropine-treated groups also had a greater reduction than the control group. In vitro, no differences were observed in acetylcholine responses. The maximum norepinephrine chronotropic response was reduced in the treadmill-exercised and the exercise plus atropine groups. The maximum norepinephrine-induced frequency correlated with the in vitro ISF (r = 0.75). Thus, ISF was reduced with training, but this effect was independent of parasympathetic activity. The properties of the sinoatrial node which set ISF also influenced the maximum norepinephrine response.
R L Hughson; J R Sutton; J D Fitzgerald; N L Jones
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  Canadian journal of physiology and pharmacology     Volume:  55     ISSN:  0008-4212     ISO Abbreviation:  Can. J. Physiol. Pharmacol.     Publication Date:  1977 Aug 
Date Detail:
Created Date:  1977-11-25     Completed Date:  1977-11-25     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0372712     Medline TA:  Can J Physiol Pharmacol     Country:  CANADA    
Other Details:
Languages:  eng     Pagination:  813-20     Citation Subset:  IM    
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MeSH Terms
Acetylcholine / pharmacology
Atropine / pharmacology
Body Weight
Carbachol / pharmacology
Heart / drug effects
Heart Rate* / drug effects
Myocardium / metabolism
Norepinephrine / pharmacology*
Organ Size / drug effects
Physical Exertion*
Potassium / metabolism
Sinoatrial Node / physiology*
Sodium / metabolism
Time Factors
Reg. No./Substance:
51-41-2/Norepinephrine; 51-55-8/Atropine; 51-83-2/Carbachol; 51-84-3/Acetylcholine; 7440-09-7/Potassium; 7440-23-5/Sodium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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