Effects of spinal section and of positive-feedback excitatory reflex on sympathetic and heart rate variability

Nicola Montano, Chiara Cogliati, Valdo Jose Dias Da Silva, Tomaso Gnecchi-Ruscone, Marcello Massimini, Alberto Porta, Alberto Malliani

Research output: Contribution to journalArticle

Abstract

The sympathetic outflow appears to be capable of displaying a rhythmicity synchronous with cardiovascular Mayer's waves even after spinal section. To test the hypothesis that spinal sympathetic low frequency (LF) oscillation can be enhanced during sympathetic excitation, we recorded cardiac sympathetic nerve activity (SNA), R-R interval, arterial pressure, and ventilation in 9 unanesthetized decerebrate-vagotomized cats before and after C1 spinal section. LF and high frequency (HF) components were detected in the variability of SNA, R-R interval, and systolic arterial pressure both before and after spinal section. In this latter condition, a significant coherence between LF(SNA) and LF(R-R) was present in 5 animals, whereas HF(SNA) and HF(R-R) were correlated in 4 animals. During an excitatory sympathetic spinal reflex elicited by aortic constriction, the efferent sympathetic firing was markedly enhanced (from 7±2 to 33±7 spikes/s); concomitantly, the powers of both LF(SNA) and HF(SNA) were also increased. Coherence between LF(SNA) and LF(R-R) became significant in all cases, whereas HF(SNA) and HF(R-R) became correlated in 6 animals. In 3 animals, the reflex sympathetic excitation was no longer elicitable after interrupting a vast contingent of sympathetic afferents by means of thoracic dorsal root section. We report for the first time that LF and HF oscillations are detectable in SNA, R-R interval, and systolic arterial pressure variabilities of decerebrate-vagotomized spinal cats and that an excitatory spinal reflex is capable of increasing the power of both SNA spectral components.

Original languageEnglish
Pages (from-to)1029-1034
Number of pages6
JournalHypertension
Volume36
Issue number6
Publication statusPublished - 2000

Keywords

  • Autonomic nervous system
  • Heart
  • Reflex
  • Sympathetic nervous system

ASJC Scopus subject areas

  • Internal Medicine

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