Document Detail

The influence of heart rate on baroreceptor fibre activity in the carotid sinus and aortic depressor nerves of the rabbit.
MedLine Citation:
PMID:  16740639     Owner:  NLM     Status:  MEDLINE    
The arterial baroreceptors and their afferent fibres provide the sensory arm of the reflex that regulates systemic arterial pressure. We have examined whether the relationship between mean baroreceptor discharge and mean arterial pressure is altered when heart rate changes. Experiments were performed on pentobarbitone-anaesthetized rabbits. We recorded the activity of single and multifibre preparations of the carotid sinus (CSN) and aortic depressor nerves (ADN). Data were collected under control conditions and while heart rate was increased by approximately 30-35% by right atrial pacing. Baroreceptor regions were exposed to ramps of pressure (from approximately 25 to 140 mmHg, at approximately 0.5-1 mmHg s(-1)), generated by inflation and deflation of cuffs placed around the inferior vena cava and descending thoracic aorta. Response curves relating baroreceptor discharge to mean pressure were constructed and fitted with third-order polynomial expressions. To provide a measure of an effect of an increase in heart rate on the response curve in the region of the normal operating pressure, we calculated the position of the test response curve relative to the position of the control curve at 90 mmHg (deltaBP(90)). For the ADN, the activity of single fibres (presumptive myelinated fibres) was unaffected by increasing heart rate (deltaBP(90) = +0.1 +/- 1.0 mmHg), while single fibres in the CSN showed a small increase in activity (deltaBP(90) = -1.5 +/- 0.3 mmHg). In multifibre preparations there was a small increase in activity that may be attributable to additional activity in unmyelinated fibres (ADN, deltaBP(90) = -3.4 +/- 1.2 mmHg; CSN, deltaBP(90) = -5.2 +/- 0.9 mmHg). We conclude that the mean discharge of arterial baroreceptors remains a reliable index of mean arterial pressure in the presence of substantial changes in heart rate.
Carolyn J Barrett; Chris P Bolter
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-06-01
Journal Detail:
Title:  Experimental physiology     Volume:  91     ISSN:  0958-0670     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2006 Sep 
Date Detail:
Created Date:  2006-09-01     Completed Date:  2006-10-30     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  845-52     Citation Subset:  IM    
Department of Physiology, University of Otago, Dunedin, New Zealand.
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MeSH Terms
Aorta / innervation*
Blood Pressure / physiology
Carotid Sinus / innervation*
Heart Rate / physiology*
Nerve Fibers / physiology*
Neurons, Afferent / physiology
Pressoreceptors / physiology*

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