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Simulated microgravity produces attenuated baroreflex-mediated pressor, chronotropic, and inotropic responses in mice.

Publication ,  Journal Article
Jung, AS; Harrison, R; Lee, KH; Genut, J; Nyhan, D; Brooks-Asplund, EM; Shoukas, AA; Hare, JM; Berkowitz, DE
Published in: Am J Physiol Heart Circ Physiol
August 2005

Whether myocardial contractile impairment contributes to orthostatic intolerance (OI) is controversial. Accordingly, we used transient bilateral carotid occlusion (TBCO) to compare the in vivo pressor, chronotropic, and inotropic responses (parts 1 and 2) to open-loop selective carotid baroreceptor unloading in anesthetized mice. In part 3, in vitro myocyte responses to isoproterenol in mice exposed to hindlimb unweighting (HLU) for approximately 2 wk were determined. Heart rate (HR) and mean arterial pressure (MAP) responses to TBCO were measured. In control mice, TBCO increased HR (15 +/- 2 beats/min, P < 0.05) and MAP (17 +/- 2 mmHg, P < 0.05). These responses were markedly potentiated in denervated control (DC) mice, in which the aortic depressor nerve and sympathetic trunk were sectioned before measurement. Baroreflex responses to TBCO were eliminated by blockade with hexamethonium bromide (10 microg/kg). In HLU (denervated) mice, HR and MAP responses were reduced approximately 70% compared with DC mice. In part 2, myocardial contractile responses to TBCO were measured with a left ventricular micromanometer-conductance catheter. TBCO in DC mice increased the slope of the end-systolic pressure-volume relation (end-systolic elastance) by 86 +/- 13%. This inotropic response was attenuated (14 +/- 10%, P < 0.005) after HLU. In part 3, contractile responses to isoproterenol were impaired in myocytes isolated from HLU mice. In conclusion, selective carotid baroreceptor unloading stimulates HR, blood pressure, and myocardial contractility, and HLU attenuates each response. These findings have important implications for the management of OI in astronauts, the elderly, and individuals subjected to prolonged bed rest.

Duke Scholars

Published In

Am J Physiol Heart Circ Physiol

DOI

ISSN

0363-6135

Publication Date

August 2005

Volume

289

Issue

2

Start / End Page

H600 / H607

Location

United States

Related Subject Headings

  • Weightlessness Simulation
  • Myocytes, Cardiac
  • Myocardial Contraction
  • Mice, Inbred C57BL
  • Mice
  • Isoproterenol
  • Heart Rate
  • Carotid Stenosis
  • Cardiovascular System & Hematology
  • Cardiotonic Agents
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Jung, A. S., Harrison, R., Lee, K. H., Genut, J., Nyhan, D., Brooks-Asplund, E. M., … Berkowitz, D. E. (2005). Simulated microgravity produces attenuated baroreflex-mediated pressor, chronotropic, and inotropic responses in mice. Am J Physiol Heart Circ Physiol, 289(2), H600–H607. https://doi.org/10.1152/ajpheart.01091.2004
Jung, Albert S., Robert Harrison, Kwang H. Lee, Jordan Genut, Daniel Nyhan, E. M. Brooks-Asplund, Artin A. Shoukas, Joshua M. Hare, and Dan E. Berkowitz. “Simulated microgravity produces attenuated baroreflex-mediated pressor, chronotropic, and inotropic responses in mice.Am J Physiol Heart Circ Physiol 289, no. 2 (August 2005): H600–607. https://doi.org/10.1152/ajpheart.01091.2004.
Jung AS, Harrison R, Lee KH, Genut J, Nyhan D, Brooks-Asplund EM, et al. Simulated microgravity produces attenuated baroreflex-mediated pressor, chronotropic, and inotropic responses in mice. Am J Physiol Heart Circ Physiol. 2005 Aug;289(2):H600–7.
Jung, Albert S., et al. “Simulated microgravity produces attenuated baroreflex-mediated pressor, chronotropic, and inotropic responses in mice.Am J Physiol Heart Circ Physiol, vol. 289, no. 2, Aug. 2005, pp. H600–07. Pubmed, doi:10.1152/ajpheart.01091.2004.
Jung AS, Harrison R, Lee KH, Genut J, Nyhan D, Brooks-Asplund EM, Shoukas AA, Hare JM, Berkowitz DE. Simulated microgravity produces attenuated baroreflex-mediated pressor, chronotropic, and inotropic responses in mice. Am J Physiol Heart Circ Physiol. 2005 Aug;289(2):H600–H607.

Published In

Am J Physiol Heart Circ Physiol

DOI

ISSN

0363-6135

Publication Date

August 2005

Volume

289

Issue

2

Start / End Page

H600 / H607

Location

United States

Related Subject Headings

  • Weightlessness Simulation
  • Myocytes, Cardiac
  • Myocardial Contraction
  • Mice, Inbred C57BL
  • Mice
  • Isoproterenol
  • Heart Rate
  • Carotid Stenosis
  • Cardiovascular System & Hematology
  • Cardiotonic Agents