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Trends in Comparative Biochemistry & Physiology   Volumes    Volume 17 
Spontaneous fluctuations of renal and lumbar sympathetic nerve activities in conscious rats
Claude Julien
Pages: 35 - 43
Number of pages: 9
Trends in Comparative Biochemistry & Physiology
Volume 17 

Copyright © 2013 Research Trends. All rights reserved

The present study compared the spontaneous fluctuations of renal sympathetic nerve activity (SNA) and lumbar SNA in conscious rats. Renal and lumbar SNAs were simultaneously recorded in 6 freely behaving rats during approximately 4 h. The relation between spontaneous fluctuations of SNAs was assessed by computing regression lines relating 1-min average values of SNAs. Although significant (P = 0.0017 ± 0.0015), the coefficients of determination revealed a rather low level of shared variance between SNAs (r2 = 0.107 ± 0.029). Similarly, coherence (a measure of linear coupling in the frequency domain) did not reach significance for fluctuations lasting from ~5 s to 54.6 min. However, for oscillations associated with arterial pressure Mayer waves (oscillations generated by the baroreflex with period near 2.5 s), coherence peaked at 0.78 ± 0.04, thus revealing a strong linear coupling. Coherence was also significant (0.54 ± 0.05) in the band containing respiratory frequencies (usually between 1 and 2 Hz). Mathematically removing the influence of arterial pressure eliminated the relationship between SNAs at Mayer wave’s frequency, thus pointing to a common baroreflex origin for oscillations of both SNAs. In addition, both SNAs were tightly coupled during drug-induced changes in arterial pressure. We conclude that spontaneous, slow fluctuations of renal and lumbar SNAs are mostly dissociated, although they vary in a coordinated way during both spontaneous and forced baroreflex solicitation. These findings argue for caution in extrapolations from one regional SNA to overall sympathetic outflow.
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