Influence of increased plasma osmolality on sympathetic outflow during apnea

Jody Leigh Greaney, Chester A. Ray, Allen V. Prettyman, David G. Edwards, William B. Farquhar

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Animal models have shown that peripheral chemoreceptors alter their firing patterns in response to changes in plasma osmolality, which, in turn, may modulate sympathetic outflow. The purpose of this study was to test the hypothesis that increases in plasma osmolality augment muscle sympathetic nerve activity (MSNA) responses to chemoreceptor activation. MSNA was recorded from the peroneal nerve (microneurography) during a 23-min intravenous hypertonic saline infusion (3% NaCl; HSI). Chemoreceptor activation was elicited by voluntary end-expiratory apnea. MSNA responses to end-expiratory apnea were calculated as the absolute increase from the preceding baseline period. Plasma osmolality significantly increased from pre- to post-HSI (284 ± 1 to 290 ± 1 mOsm/kg H2O; P < 0.01). There was a significant overall effect of osmolality on sympathetic activity (P < 0.01). Duration of the voluntary end-expiratory apnea was not different after HSI (pre = 40 ± 5 s; post = 41 ± 4 s). MSNA responses to end-expiratory apnea were not different after HSI, expressed as an absolute change in burst frequency (n = 11; pre = 8 ± 2; post = 11 ± 1 burst/min) and as a percent increase in total activity (pre = 51 ± 4% AU; post = 53 ± 4% AU). A second group of subjects (n = 8) participated in 23-min volume/time-control intravenous isotonic saline infusions (0.9% NaCl). Isotonic saline volume-control infusions yielded no change in plasma osmolality or MSNA at rest. Furthermore, MSNA responses to apnea following isotonic saline infusion were not different. In summary, elevated plasma osmolality increased MSNA at rest and during apnea, but contrary to the hypothesis, MSNA responsiveness to apnea was not augmented. Therefore, this study does not support a neural interaction between plasma osmolality and chemoreceptor stimulation.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume299
Issue number4
DOIs
StatePublished - Oct 1 2010

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Apnea
Osmolar Concentration
Muscles
Peroneal Nerve
Animal Models

All Science Journal Classification (ASJC) codes

  • Physiology
  • Physiology (medical)

Cite this

Greaney, Jody Leigh ; Ray, Chester A. ; Prettyman, Allen V. ; Edwards, David G. ; Farquhar, William B. / Influence of increased plasma osmolality on sympathetic outflow during apnea. In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology. 2010 ; Vol. 299, No. 4.
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abstract = "Animal models have shown that peripheral chemoreceptors alter their firing patterns in response to changes in plasma osmolality, which, in turn, may modulate sympathetic outflow. The purpose of this study was to test the hypothesis that increases in plasma osmolality augment muscle sympathetic nerve activity (MSNA) responses to chemoreceptor activation. MSNA was recorded from the peroneal nerve (microneurography) during a 23-min intravenous hypertonic saline infusion (3{\%} NaCl; HSI). Chemoreceptor activation was elicited by voluntary end-expiratory apnea. MSNA responses to end-expiratory apnea were calculated as the absolute increase from the preceding baseline period. Plasma osmolality significantly increased from pre- to post-HSI (284 ± 1 to 290 ± 1 mOsm/kg H2O; P < 0.01). There was a significant overall effect of osmolality on sympathetic activity (P < 0.01). Duration of the voluntary end-expiratory apnea was not different after HSI (pre = 40 ± 5 s; post = 41 ± 4 s). MSNA responses to end-expiratory apnea were not different after HSI, expressed as an absolute change in burst frequency (n = 11; pre = 8 ± 2; post = 11 ± 1 burst/min) and as a percent increase in total activity (pre = 51 ± 4{\%} AU; post = 53 ± 4{\%} AU). A second group of subjects (n = 8) participated in 23-min volume/time-control intravenous isotonic saline infusions (0.9{\%} NaCl). Isotonic saline volume-control infusions yielded no change in plasma osmolality or MSNA at rest. Furthermore, MSNA responses to apnea following isotonic saline infusion were not different. In summary, elevated plasma osmolality increased MSNA at rest and during apnea, but contrary to the hypothesis, MSNA responsiveness to apnea was not augmented. Therefore, this study does not support a neural interaction between plasma osmolality and chemoreceptor stimulation.",
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Influence of increased plasma osmolality on sympathetic outflow during apnea. / Greaney, Jody Leigh; Ray, Chester A.; Prettyman, Allen V.; Edwards, David G.; Farquhar, William B.

In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol. 299, No. 4, 01.10.2010.

Research output: Contribution to journalArticle

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