Coupled oscillators account for the slow rhythms in sympathetic
nerve discharge and phrenic nerve activity.
Zhong, Sheng, Shi-Yi Zhou, Gerard L. Gebber, and Susan M. Barman.
Departments of Pharmacology/Toxicology and Physiology, Michigan
State University, East Lansing, MI 48824
APStracts 3:0400R, 1996.
Phase-locked slow rhythms in sympathetic nerve discharge (SND) and
phrenic nerve activity (PNA) are generally thought to arise from a
common brain stem "cardiorespiratory" oscillator. The
results obtained in vagotomized and baroreceptor-denervated cats
anesthetized with pentobarbital do not support this view. First,
partial coherence analysis revealed that the discharges of pairs of
sympathetic nerves remained correlated at the frequency of the
central respiratory cycle after mathematical removal of the portion
of these signals common to PNA. The residual coherence suggests that
the slow rhythm in SND is dependent on central mechanisms in addition
to those responsible for rhythmic PNA. Second, the rhythms in SND and
PNA became coupled in a 2:1 relation during either moderate systemic
hypocapnia or hypercapnia. Third, the slow rhythm in SND was
maintained when rhythmic PNA was eliminated during extreme
hypocapnia. Fourth, during extreme hypercapnia, coherence of the
rhythms in SND and PNA was drastically reduced. These results suggest
that the slow rhythms in SND and PNA arise from separate oscillators
that are normally coupled.
Received 7 August 1996; accepted in final form 24 October 1996.
APS Manuscript Number R473-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996