Document Detail

Inotropic responses of the left ventricle to changes in heart rate in anesthetized rabbits.
MedLine Citation:
PMID:  2882829     Owner:  NLM     Status:  MEDLINE    
Factors known to influence left ventricular contractility include preload, afterload, circulating catecholamine concentration, efferent sympathetic discharge, and heart rate. Heart rate influences have been primarily determined in the dog, whereas the influence of heart rate in smaller mammals has not been determined. Eight pentobarbital-anesthetized rabbits were instrumented to measure electrocardiogram, heart rate, left ventricular pressure, end-diastolic pressure, dP/dt, and mean and pulsatile aortic pressures. Systematic bradycardia was induced by stimulating the peripheral end of the sectioned right vagus nerve. Between 293 and 235 beats/min, there was no change in (dP/dt)max as heart rate was decreased. Below this range there was a direct relationship between (dP/dt)max and heart rate. Preload remained unchanged down to 132 beats/min. There was a small but significant decrease in afterload (0.09 mmHg X beat-1 X min-1; 1 mmHg = 133.32 Pa) throughout the decrease in heart rate. Infusion of propranolol (2.0 mg/kg) produced no marked change in the heart rate - (dP/dt)max relationship, although both resting heart rate and (dP/dt)max were reduced. This study demonstrates that (dP/dt)max is not influenced by changes in heart rate above 235 beats/min in the pentobarbital-anesthetized rabbit. These results differ from findings in other animals, and demonstrate that species and heart rate ranges must be considered when drawing conclusions regarding (dP/dt)max as a reliable index of contractility.
L B Bell; D F Peterson
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Canadian journal of physiology and pharmacology     Volume:  65     ISSN:  0008-4212     ISO Abbreviation:  Can. J. Physiol. Pharmacol.     Publication Date:  1987 Feb 
Date Detail:
Created Date:  1987-06-17     Completed Date:  1987-06-17     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0372712     Medline TA:  Can J Physiol Pharmacol     Country:  CANADA    
Other Details:
Languages:  eng     Pagination:  179-84     Citation Subset:  IM    
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MeSH Terms
Adrenergic beta-Antagonists / pharmacology
Catecholamines / physiology
Electric Stimulation
Heart Rate / drug effects*
Myocardial Contraction / drug effects*
Propranolol / pharmacology
Vagus Nerve / physiology
Reg. No./Substance:
0/Adrenergic beta-Antagonists; 0/Catecholamines; 525-66-6/Propranolol

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

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