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The influence of heart rate on baroreceptor fibre activity in the carotid sinus and aortic depressor nerves of the rabbit
Author(s) -
Barrett Carolyn J.,
Bolter Chris P.
Publication year - 2006
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2006.033902
Subject(s) - baroreceptor , carotid sinus , cardiology , heart rate , anatomy , medicine , aortic sinus , aorta , blood pressure
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 ∼30–35% by right atrial pacing. Baroreceptor regions were exposed to ramps of pressure (from ∼25 to 140 mmHg, at ∼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 (δBP 90 ). For the ADN, the activity of single fibres (presumptive myelinated fibres) was unaffected by increasing heart rate (δBP 90 =+0.1 ± 1.0 mmHg) , while single fibres in the CSN showed a small increase in activity (δBP 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, δBP 90 =−3.4 ± 1.2 mmHg ; CSN, δBP 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.