HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) 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 Coleridge, H M Articles by Schultz, H D Search for Related Content PubMed PubMed Citation Articles by Coleridge, H M Articles by Schultz, H D

Cardiovascular Research Institute, University of California, San Francisco 94143-0130.

1. We compared the pressure-response characteristics of C fibre and A fibre baroreceptors in the carotid sinus of anaesthetized dogs, recording impulses from the sinus nerve and varying mean pressure in the vascularly isolated sinus, which was distended with a pulsatile pressure. Functional stimulus-response curves were obtained by gradually increasing sinus pressure above and decreasing it below a set-point of 100 mmHg. Baroreceptors were identified by a pulsatile discharge synchronous with the pulsations in sinus pressure. A and C fibre baroreceptors were identified by the conduction velocities and blocking temperatures of their axons. 2. The pressure-response characteristics of C and A fibre baroreceptors differed in several respects. C fibres had a pulsatile firing threshold 50 mmHg higher than that of A fibres (105.8 +/- 1.8 and 54.6 +/- 2.9 mmHg, respectively), an average maximal sensitivity 35% of that of A fibres (0.39 and 1.12 impulses s-1 mmHg-1, respectively), and a maximal frequency (at 220 mmHg) 29% of that of A fibres (24.5 and 84.3 impulses/s, respectively). Although invariably pulsatile at pressures above threshold, the firing pattern of C fibre baroreceptors tended to be more irregular than that of their A fibre counterparts. 3. Impulses were also recorded from C fibres that were stimulated by increasing sinus pressure but had an irregular, non-pulsatile discharge, a high pressure threshold (averaging 154.1 +/- 7.2 mmHg), and a low maximum frequency (10.8 +/- 2.4 impulses/s). 4. Cooling the sinus nerve progressively attenuated conduction in both A and C fibres, A fibres being blocked between 12 and 4 degrees C (mean 6.8 degrees C) and C fibres between 4 and -1.5 degrees C (mean 1.0 degree C). Although cooling the sinus nerve to 7 degrees C did not block conduction in all A fibres, impulse activity in baroreceptor A fibres at a carotid sinus pressure of 200 mmHg was no greater than that at a pressure of 75 mmHg. By contrast, at 7 degrees C baroreceptor C fibres still provided a signal proportional to sinus pressure. 5. Our results suggest that A and C fibre baroreceptors subserve different reflex functions, the former signalling changes in arterial pressure both above and below the normal set-point, the latter only changes above. They also suggest that differential cold blockade may be a useful tool to determine the contribution of C fibre baroreceptors to cardiovascular reflexes.

This article has been cited by other articles:

				B. Feng, B.-y. Li, E. A. Nauman, and J. H. Schild Theoretical and electrophysiological evidence for axial loading about aortic baroreceptor nerve terminals in rats Am J Physiol Heart Circ Physiol, December 1, 2007; 293(6): H3659 - H3672. [Abstract] [Full Text] [PDF]

				C. J. Barrett and S. C. Malpas Problems, possibilities, and pitfalls in studying the arterial baroreflexes' influence over long-term control of blood pressure Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2005; 288(4): R837 - R845. [Abstract] [Full Text] [PDF]

				T. E. Lohmeier, E. D. Irwin, M. A. Rossing, D. J. Serdar, and R. S. Kieval Prolonged Activation of the Baroreflex Produces Sustained Hypotension Hypertension, February 1, 2004; 43(2): 306 - 311. [Abstract] [Full Text] [PDF]

				S. C. Malpas What sets the long-term level of sympathetic nerve activity: is there a role for arterial baroreceptors? Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2004; 286(1): R1 - R12. [Abstract] [Full Text] [PDF]

				A. Balkowiec and D. M. Katz Activity-Dependent Release of Endogenous Brain-Derived Neurotrophic Factor from Primary Sensory Neurons Detected by ELISA In Situ J. Neurosci., October 1, 2000; 20(19): 7417 - 7423. [Abstract] [Full Text] [PDF]

				W. Fan and M. C. Andresen Differential frequency-dependent reflex integration of myelinated and nonmyelinated rat aortic baroreceptors Am J Physiol Heart Circ Physiol, August 1, 1998; 275(2): H632 - H640. [Abstract] [Full Text] [PDF]