Relative contributions of cardiopulmonary and sinoaortic baroreflexes in causing sympathetic activation in the human skeletal muscle circulation during orthostatic stress

Tage N. Jacobsen, Barbara J. Morgan, Urs Scherrer, Susanne F. Vissing, Richard A. Lange, Nancy Johnson, W. Steves Ring, Peter S. Rahko, Peter Hanson, Ronald G. Victor

Research output: Contribution to journalArticle

95 Scopus citations

Abstract

The aim of this study was to reexamine the hypothesis that cardiopulmonary baroreflexes are more important than sinoaortic baroreflexes in causing vasoconstriction in the skeletal muscle circulation during orthostatic stress. We recorded muscle sympathetic nerve activity (MSNA) with microelectrodes in the peroneal nerve (and forearm blood flow with venous occlusion plethysmography) in normal subjects (innervated ventricles) and in heart transplant recipients (denervated ventricles) during graded lower body negative pressure (LBNP) performed alone and in combination with intravenous infusion of phenylephrine, which was titrated to eliminate the orthostatically induced fall in blood pressure and thus the unloading of both carotid and aortic baroreceptors. The principal new findings are as follows: (1) The increases in both MSNA and forearm vascular resistance during multiple levels of LBNP were not attenuated by heart transplantation, which causes ventricular but not sinoaortic deafferentation. (2) In heart transplant recipients, a small increase in MSNA during mild LBNP was dependent on a decrease in arterial pressure, but in normal subjects, a similar increase in MSNA occurred in the absence of any detectable decrease in the aortic pressure stimulus to the sinoaortic baroreceptors. (3) In normal subjects, the large increase in MSNA during a high level of LBNP was dependent on a decrease in arterial pressure and could be dissociated from the decrease in central venous pressure. Taken together, the findings strongly suggest that sinoaortic baroreflexes are much more important and ventricular baroreflexes are much less important than previously thought in causing reflex sympathetic activation and vasoconstriction in the human skeletal muscle circulation during orthostatic stress.

Original languageEnglish (US)
Pages (from-to)367-378
Number of pages12
JournalCirculation research
Volume73
Issue number2
DOIs
StatePublished - Jan 1 1993

Keywords

  • baroreceptor reflexes
  • sympathetic nervous system
  • ventricular sensory receptors

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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