Discharge Pattern of Renal Sympathetic Nerve Activity in the Conscious Rat: Spectral Analysis of Integrated Activity

• Published in: Journal of neurophysiology Vol. 84; no. 6; pp. 2859 - 2867
• Main Authors: Kunitake, Takato, Kannan, Hiroshi
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01-12-2000
• Subjects: Action Potentials - drug effects; Action Potentials - physiology; Animals; Fourier Analysis; Heart Rate - physiology; Kidney - innervation; Male; Nitroprusside - pharmacology; Periodicity; Pressoreceptors - drug effects; Pressoreceptors - physiology; Pressoreceptors - surgery; Rats; Rats, Wistar; Respiration; Signal Processing, Computer-Assisted; Sympathectomy; Sympathetic Nervous System - drug effects; Sympathetic Nervous System - physiology; Vasodilator Agents - pharmacology; Wakefulness - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.2000.84.6.2859

Department of Physiology, Miyazaki Medical College, Miyazaki
889-1692, Japan
Kunitake, Takato and
Hiroshi Kannan.
Discharge Pattern of Renal Sympathetic Nerve Activity in the
Conscious Rat: Spectral Analysis of Integrated Activity. J. Neurophysiol. 84: 2859-2867, 2000. We investigated
the periodic characteristics of bursting discharge in renal sympathetic
nerve activity (RSNA) in conscious rats. Employing a discrete fast
Fourier transform algorithm, a power spectrum analysis was used to
quantify periodicities present in rectified and integrated RSNA whose
signal-to-noise ratio in the recordings was greater than six. In
conscious rats with intact baroreceptors, RSNA was characterized by
four frequency components occurring at about 0.5, 1.5, 6, and 12 Hz,
which corresponded to the low-frequency fluctuation of heart rate,
respiration, and frequency of heart beat, and its harmonics,
respectively. After intravenous infusion of sodium nitroprusside (SNP)
to elicit reflex increases in RSNA and heart rate, the power for the
component at 6 Hz followed the changes in heart beat frequency and was
significantly increased, while those for the three other components
were attenuated or experienced no change. In sino-aortic denervated
(SAD) conscious rats, all four components were abolished, and the power
spectrum was well fitted by a flat or Lorentzian curve, suggesting an
almost random pattern. Only a respiratory-related component, which
suggested common central modulation, appeared sporadically for short
periods but was absent for the most part. Therefore most of this
component together with the low-frequency component was also likely due to the baroreceptor-dependent peripheral modulation. The activity was
sorted in 15 subgroups on the basis of spike amplitudes in the RSNA.
Each subgroup showed frequency characteristics similar to the whole
nerve activity. These results suggest that all periodicity in the RSNA
of conscious rats with intact baroreceptors is caused by the
baroreceptor input.