Coupled oscillators account for the slow rhythms in sympathetic nerve discharge and phrenic nerve activity.
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 sodium 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 relationship 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.
Zhong
S
S
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824, USA.
Zhou
S Y
SY
Gebber
G L
GL
Barman
S M
SM
D000204:Activity Cycles; D000818:Animals; D001933:Brain Stem / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D002415:Cats; D003714:Denervation; D006321:Heart / Q000294:innervation; D006706:Homeostasis; D007668:Kidney / Q000294:innervation; D009474:Neurons / Q000502:physiology; D009991:Oscillometry; D010791:Phrenic Nerve / Q000502:physiology*; D011311:Pressoreceptors / Q000502:physiology; D012044:Regression Analysis; D012119:Respiration / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology; D013154:Spleen / Q000294:innervation; D013564:Sympathetic Nervous System / Q000502:physiology*; D014628:Vagotomy
D002245:Carbon Dioxide