Relationship between muscle sympathetic nerve activity and systemic hemodynamics during nitric oxide synthase inhibition in humans

N. Charkoudian, M. J. Joyner, S. A. Barnes, C. P. Johnson, J. H. Eisenach, N. M. Dietz, B. G. Wallin

Research output: Contribution to journalArticle

44 Scopus citations

Abstract

Large interindividual differences exist in resting sympathetic nerve activity (SNA) among normotensive humans with similar arterial pressure (AP). We recently showed inverse relationships of resting SNA with cardiac output (CO) and vascular adrenergic responsiveness that appear to balance the influence of differences in SNA on blood pressure. In the present study, we tested whether nitric oxide (NO)-mediated vasodilation has a role in this balance by evaluating hemodynamic responses to systemic NO synthase (NOS) inhibition in individuals with low and high resting muscle SNA (MSNA). We measured MSNA via peroneal microneurography, CO via acetylene uptake and AP directly, at baseline and during increasing systemic doses of the NOS inhibitor NG-monomethyl- L-arginine (L-NMMA). Baseline MSNA ranged from 9 to 38 bursts/min (13 to 68 bursts/100 heartbeats). L-NMMA caused dose-dependent increases in AP and total peripheral resistance and reflex decreases in CO and MSNA. Increases in AP with L-NMMA were greater in individuals with high baseline MSNA (PANOVA = 0.05). For example, after 8.5 mg/kg of L-NMMA, in the low MSNA subgroup (n = 6, 28 ± 4 bursts/100 heartbeats), AP increased 9 ± 1 mmHg, whereas in the high-MSNA subgroup (n = 6, 58 ± 3 bursts/100 heartbeats), AP increased 15 ± 2 mmHg (P < 0.01). The high-MSNA subgroup had lower baseline CO and smaller decreases in CO with L-NMMA, but changes in total peripheral resistance were not different between groups. We conclude that differences in CO among individuals with varying sympathetic traffic have important hemodynamic implications during disruption of NO-mediated vasodilation.

Original languageEnglish (US)
Pages (from-to)H1378-H1383
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume291
Issue number3
DOIs
StatePublished - Sep 13 2006

Keywords

  • Cardiac output
  • Hypertension
  • Sympathetic nervous system

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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