Static interaction between muscle mechanoreflex and arterial baroreflex in determining efferent sympathetic nerve activity

Kenta Yamamoto, Toru Kawada, Atsunori Kamiya, Hiroshi Takaki, Masaru Sugimachi, Kenji Sunagawa

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

Elucidation of the interaction between the muscle mechanoreflex and the arterial baroreflex is essential for better understanding of sympathetic regulation during exercise. We characterized the effects of these two reflexes on sympathetic nerve activity (SNA) in anesthetized rabbits (n = 7). Under open-loop baroreflex conditions, we recorded renal SNA at carotid sinus pressure (CSP) of 40, 80, 120, or 160 mmHg while passively stretching the hindlimb muscle at muscle tension (MT) of 0, 2, 4, or 6 kg. The MT-SNA relationship at CSP of 40 mmHg approximated a straight line. Increase in CSP from 40 to 120 and 160 mmHg shifted the MT-SNA relationship downward and reduced the response range (the difference between maximum and minimum SNA) to 43 ± 10% and 19 ± 6%, respectively (P < 0.01). The CSP-SNA relationship at MT of 0 kg approximated a sigmoid curve. Increase in MT from 0 to 2, 4, and 6 kg shifted the CSP-SNA relationship upward and extended the response range to 133 ± 8%, 156 ± 14%, and 178 ± 15%, respectively (P < 0.01). A model of algebraic summation, i.e., parallel shift, with a threshold of SNA functionally reproduced the interaction of the two reflexes (y = 1.00x - 0.01; r2 = 0.991, root mean square = 2.6% between estimated and measured SNA). In conclusion, the response ranges of SNA to baroreceptor and muscle mechanoreceptor input changed in a manner that could be explained by a parallel shift with threshold.

Original languageEnglish
Pages (from-to)H1604-H1609
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume289
Issue number4 58-4
DOIs
Publication statusPublished - Oct 2005

Keywords

  • Exercise
  • Exercise pressor reflex
  • Muscle stretch
  • Subliminal fringe

ASJC Scopus subject areas

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

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