Baroreflex control of muscle sympathetic nerve activity: A nonpharmacological measure of baroreflex sensitivity

Emma C. Hart, Michael J. Joyner, B. Gunnar Wallin, Tomas Karlsson, Timothy B. Curry, Nisha Charkoudian

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


The sensitivity of baroreflex control of sympathetic nerve activity (SNA) represents the responsiveness of SNA to changes in blood pressure. In a slightly different analysis, the baroreflex threshold measures the probability of whether a sympathetic burst will occur at a given diastolic blood pressure. We hypothesized that baroreflex threshold analysis could be used to estimate the sensitivity of the sympathetic baroreflex measured by the pharmacological modified Oxford test. We compared four measures of sympathetic baroreflex sensitivity in 25 young healthy participants: the "gold standard" modified Oxford analysis (nitroprusside and phenylephrine), nonbinned spontaneous baroreflex analysis, binned spontaneous baroreflex analysis, and threshold analysis. The latter three were performed during a quiet baseline period before pharmacological intervention. The modified Oxford baroreflex sensitivity was significantly related to the threshold slope (r = 0.71, P < 0.05) but not to the binned (1 mmHg bins) and the nonbinned spontaneous baroreflex sensitivity (r = 0.22 and 0.36, respectively, P > 0.05), which included burst area. The threshold analysis was also performed during the modified Oxford manipulation. Interestingly, we found that the threshold analysis results were not altered by the vasoactive drugs infused for the modified Oxford. We conclude that the noninvasive threshold analysis technique can be used as an indicator of muscle SNA baroreflex sensitivity as assessed by the modified Oxford technique. Furthermore, the modified Oxford method does not appear to alter the properties of the baroreflex.

Original languageEnglish (US)
Pages (from-to)H816-H822
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number3
StatePublished - Mar 2010


  • Baroreflex threshold
  • Modified oxford method
  • Spontaneous baroreflex

ASJC Scopus subject areas

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


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