In animals and humans, baroreceptor modulation of the sinus node in daily life can be studied by identification of the number of sequences in which systolic blood pressure (SBP) and pulse interval (PI) linearly decrease or increase for several beats. It is also studied by power spectral analysis of SBP and PI in regions where their powers are coherent, although, in contrast to the sequence method, whether this frequency-domain method specifically reflects the baroreceptor-heart rate reflex has not been adequately tested. We recorded intra-arterial BP for ~3.5 h in eight conscious cats, first intact and then 7-10 days after sinoaortic denervation (SAD). Sensitivity of baroreceptor-heart rate reflex was assessed in 120-s segments by the square root of the ratio of PI and SBP spectral powers () in the regions around 0.1 (MF) and 0.3 (HF) Hz, and coherence between PI and SBP spectral powers in MF and HF regions was computed. SAD increased overall SBP variability and reduced PI variability throughout the frequency range examined. SAD markedly reduced (P < 0.01) both -MF (65.6%) and -HF (79.9%) and consistently reduced the number of coherent segments [i.e., where coherence (K²) > 0.5] and average coherence values in the MF region. In the HF region, however, SAD did not alter the number of coherent segments, and although average coherence value throughout the HF band was reduced, in restricted portions of the band (different between animals), a high coherence value survived denervation. No significant changes were seen in any measured variables in five sham-operated cats. Thus the frequency-domain method specifically reflects baroreflex modulation of heart rate in the MF region only. In the HF region, in contrast, baroreflex and nonbaroreflex influences on the sinus node both contribute to a variable degree to determination of heart rate responses to BP oscillations. If used to study baroreflex function in daily life, this method should use the coefficient derived from MF data.

arterial baroreflex; blood pressure variability; heart rate variability; sequence analysis; spectral analysis

This article has been cited by other articles:

				M Di Rienzo, G Parati, A Radaelli, and P Castiglioni Baroreflex contribution to blood pressure and heart rate oscillations: time scales, time-variant characteristics and nonlinearities Phil Trans R Soc A, April 13, 2009; 367(1892): 1301 - 1318. [Abstract] [Full Text] [PDF]

				D. Rubinger, R. Backenroth, and D. Sapoznikov Restoration of baroreflex function in patients with end-stage renal disease after renal transplantation Nephrol. Dial. Transplant., April 1, 2009; 24(4): 1305 - 1313. [Abstract] [Full Text] [PDF]

				F. Cottin, C. Medigue, and Y. Papelier Effect of heavy exercise on spectral baroreflex sensitivity, heart rate, and blood pressure variability in well-trained humans Am J Physiol Heart Circ Physiol, September 1, 2008; 295(3): H1150 - H1155. [Abstract] [Full Text] [PDF]

				J. M. Stewart, I. Taneja, and M. S. Medow Reduced central blood volume and cardiac output and increased vascular resistance during static handgrip exercise in postural tachycardia syndrome Am J Physiol Heart Circ Physiol, September 1, 2007; 293(3): H1908 - H1917. [Abstract] [Full Text] [PDF]

				P. Castiglioni, M. Di Rienzo, A. Veicsteinas, G. Parati, and G. Merati Mechanisms of blood pressure and heart rate variability: an insight from low-level paraplegia Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2007; 292(4): R1502 - R1509. [Abstract] [Full Text] [PDF]

				J. M. Stewart, L. D. Montgomery, J. L. Glover, and M. S. Medow Changes in regional blood volume and blood flow during static handgrip Am J Physiol Heart Circ Physiol, January 1, 2007; 292(1): H215 - H223. [Abstract] [Full Text] [PDF]

				G. Parati, G. Mancia, M. D. Rienzo, P. Castiglioni, J. A. Taylor, and P. Studinger Point:Counterpoint: Cardiovascular variability is/is not an index of autonomic control of circulation J Appl Physiol, August 1, 2006; 101(2): 676 - 682. [Abstract] [Full Text] [PDF]

				R. Fazan Jr., M. de Oliveira, V. J. Dias da Silva, L. F. Joaquim, N. Montano, A. Porta, M. W. Chapleau, and H. C. Salgado Frequency-dependent baroreflex modulation of blood pressure and heart rate variability in conscious mice Am J Physiol Heart Circ Physiol, November 1, 2005; 289(5): H1968 - H1975. [Abstract] [Full Text] [PDF]

				G. Parati, M. Di Rienzo, P. Castiglioni, M. Bouhaddi, C. Cerutti, A. Cividjian, J.-L. Elghozi, J.-O. Fortrat, A. Girard, B. J.A. Janssen, et al. Assessing the Sensitivity of Spontaneous Baroreflex Control of the Heart: Deeper Insight Into Complex Physiology * Response Hypertension, May 1, 2004; 43(5): e32 - e34. [Full Text] [PDF]

				F Conci, M Di Rienzo, and P Castiglioni Blood pressure and heart rate variability and baroreflex sensitivity before and after brain death J. Neurol. Neurosurg. Psychiatry, November 1, 2001; 71(5): 621 - 631. [Abstract] [Full Text] [PDF]

				G. Nollo, A. Porta, L. Faes, M. Del Greco, M. Disertori, and F. Ravelli Causal linear parametric model for baroreflex gain assessment in patients with recent myocardial infarction Am J Physiol Heart Circ Physiol, April 1, 2001; 280(4): H1830 - H1839. [Abstract] [Full Text] [PDF]