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This Article Full Text Full Text (PDF) All Versions of this Article: 91/5/845    most recent expphysiol.2006.033902v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Barrett, C. J. Articles by Bolter, C. P. Search for Related Content PubMed PubMed Citation Articles by Barrett, C. J. Articles by Bolter, C. P. Related Collections Cardiovascular control

¹ Department of Physiology and the Centre for Neuroscience, University of Otago, Dunedin, New Zealand

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 (BP₉₀). For the ADN, the activity of single fibres (presumptive myelinated fibres) was unaffected by increasing heart rate (BP₉₀ = +0.1 ± 1.0 mmHg), while single fibres in the CSN showed a small increase in activity (BP₉₀ = –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, BP₉₀ = –3.4 ± 1.2 mmHg; CSN, BP₉₀ = –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.

(Received 15 March 2006; accepted after revision 29 March 2006; first published online 1 June 2006)
Corresponding author C. P. Bolter: Department of Physiology, School of Medical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand. Email: chris.bolter{at}otago.ac.nz

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