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This Article Full Text Full Text (PDF) All Versions of this Article: 295/3/R719    most recent 00824.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science 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 Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Ramchandra, R. Articles by May, C. N. Search for Related Content PubMed PubMed Citation Articles by Ramchandra, R. Articles by May, C. N.

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Physiological and Molecular Mechanisms Implicated in the Neural Control of Circulation

Responses of cardiac sympathetic nerve activity to changes in circulating volume differ in normal and heart failure sheep

Howard Florey Institute, University of Melbourne, Parkville, Australia

Submitted 15 November 2007 ; accepted in final form 12 July 2008

Factors controlling cardiac sympathetic nerve activity (CSNA) in the normal state and those causing the large increase in activity in heart failure (HF) remain unclear. We hypothesized from previous clinical findings that activation of cardiac mechanoreceptors by the increased blood volume in HF may stimulate sympathetic nerve activity (SNA), particularly to the heart via cardiocardiac reflexes. To investigate the effect of volume expansion and depletion on CSNA we have made multiunit recordings of CSNA in conscious normal sheep and sheep paced into HF. In HF sheep (n = 9) compared with normal sheep (n = 9), resting levels of CSNA were significantly higher (34 ± 5 vs. 93 ± 2 bursts/100 heart beats, P < 0.05), mean arterial pressure was lower (76 ± 3 vs. 87 ± 2 mmHg; P < 0.05), and central venous pressure (CVP) was greater (3.0 ± 1.0 vs. 0.0 ± 1.0 mmHg; P < 0.05). In normal sheep (n = 6), hemorrhage (400 ml over 30 min) was associated with a significant increase in CSNA (179 ± 16%) with a decrease in CVP (2.7 ± 0.7 mmHg). Volume expansion (400 ml Gelofusine over 30 min) significantly decreased CSNA (35 ± 12%) and increased CVP (4.7 ± 1.0 mmHg). In HF sheep (n = 6) the responses of CSNA to both volume expansion and hemorrhage were severely blunted with no significant changes in CSNA or heart rate with either stimulus. In summary, these studies in a large conscious mammal demonstrate that in the normal state directly recorded CSNA increased with volume depletion and decreased with volume loading. In contrast, both of these responses were severely blunted in HF with no significant changes in CSNA during either hemorrhage or volume expansion.

heart failure; sympathetic nervous system; hemorrhage; cardiac volume

This article has been cited by other articles:

				R. Ramchandra, S. G. Hood, R. Frithiof, and C. N. May Discharge properties of cardiac and renal sympathetic nerves and their impaired responses to changes in blood volume in heart failure Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2009; 297(3): R665 - R674. [Abstract] [Full Text] [PDF]