Baroreflex control of muscle sympathetic nerve activity after 120 days of 6°head-down bed rest

Atsunori Kamiya, Satoshi Iwase, Hiroki Kitazawa, Tadaaki Mano, Olga L. Vinogradova, Irina B. Kharchenko

Research output: Contribution to journalArticlepeer-review

66 Citations (Scopus)


To examine how long-lasting microgravity simulated by 6°head-down bed rest (HDBR) induces changes in the baroreflex control of muscle sympathetic nerve activity (MSNA) at rest and changes in responses of MSNA to orthostasis, six healthy male volunteers (range 26-42 yr) participated in Valsalva maneuver and head-up tilt (HUT) tests before and after 120 days of HDBR. MSNA was measured directly using a microneurographic technique. After long-term HDBR, resting supine MSNA and heart rate were augmented. The baroreflex slopes for MSNA during Valsalva maneuver (in supine position) and during 60°HUT test, determined by least-squares linear regression analysis, were significantly steeper after than before HDBR, whereas the baroreflex slopes for R-R interval were significantly flatter after HDBR. The increase in MSNA from supine to 60°HUT was not different between before and after HDBR, but mean blood pressure decreased in 60°HUT after HDBR. In conclusion, the baroreflex control of MSNA was augmented, whereas the same reflex control of R-R interval was attenuated after 120 days of HDBR.

Original languageEnglish
Pages (from-to)R445-R452
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Issue number2 47-2
Publication statusPublished - Feb 2000
Externally publishedYes


  • Microneurography
  • Orthostatic hypotension

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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