Pathways involved in synchronization of sympathetic nerve discharge to lung inflation.
In urethane-anesthetized cats, we tested the hypothesis that sympathetic nerve discharge (SND) is synchronized to lung inflation, in part, over a vagal afferent pathway that bypasses the central respiratory oscillator. For this purpose, partial coherence analysis was used to mathematically remove the portion of the relationship between intratracheal pressure (ITP; index of lung inflation) and inferior cardiac SND that was common to that between ITP and phrenic nerve activity (PNA; index of central respiratory cycle). ITP-SND partial coherence (PNA-related component removed) at the frequency of breathing should be significantly different from zero if a bypass pathway exists. This was found to be the case in paralyzed, artificially ventilated cats when lung inflation and rhythmic PNA were coupled in various ratios (e.g. 1:1, 3:1) and in spontaneously breathing cats. As expected, surgical vagotomy eliminated ITP-SND coherence in artificially ventilated cats. These findings support the view that a portion of the relationship between ITP and SND is independent of the influences of pulmonary stretch receptors on central respiratory networks.
Zhou
Shi-Yi
SY
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824-1317, USA.
Gebber
Gerard L
GL
Zhong
Sheng
S
Barman
Susan M
SM
D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D002415:Cats; D003714:Denervation; D004594:Electrophysiology / Q000379:methods; D001239:Inhalation / Q000502:physiology*; D008168:Lung / Q000294:innervation* / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology; D011311:Pressoreceptors / Q000502:physiology; D012121:Respiration, Artificial; D012125:Respiratory Center / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D013564:Sympathetic Nervous System / Q000502:physiology*; D014628:Vagotomy; D014630:Vagus Nerve / Q000502:physiology