N. Montano et al., Effects of spinal section and of positive-feedback excitatory reflex on sympathetic and heart rate variability, HYPERTENSIO, 36(6), 2000, pp. 1029-1034
Citations number
32
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
The sympathetic outflow appears to be capable of displaying a rhythmicity s
ynchronous 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 sympathe
tic 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 variab
ility of SNA, R-R interval, and systolic arterial pressure both before and
after spinal section. In this latter condition, a significant coherence bet
ween LFSNA and LFR-R was present in 5 animals, whereas HFSNA and HFR-R were
correlated in 4 animals. During an excitatory sympathetic spinal reflex el
icited by aortic constriction, the efferent sympathetic firing was markedly
enhanced (from 7 +/- 2 to 33 +/- 7 spikes/s); concomitantly, the powers of
both LFSNA and HFSNA were also increased. Coherence between LFSNA and LFR-
R became significant in all cases, whereas HFSNA and HFR-R became correlate
d in 6 animals. In 3 animals, the reflex sympathetic excitation was no long
er elicitable after interrupting a vast contingent of sympathetic afferents
by means of thoracic dorsal root section, We report for the first time tha
t: 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 bot
h SNA spectral components.