Respiratory load compensation III. Role of spinal cord afferents

D. T. Frazier, F. Xu, L. Y. Lee, R. F. Taylor

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

In a previous study, we reported that inspiratory tracheal occlusion (TO) significantly inhibited the motor drive to the diaphragm in a decerebellated bilaterally vagotomized preparation (J. Appl, Physiol. 75:675-681, 1993). The hypothesis to be tested in the present study was that respiratory muscle afferents activated by inspiratory TO provided the inputs responsible for the observed inhibition. Adult cats were anesthetized, tracheotomized, and instrumented with diaphragm electromyographic (EMGdi) recording electrodes. The cerebellum, vagi, and dorsal spinal cord (C2-T2) were surgically exposed. Inspiratory TO was applied before and after cold blockade of the dorsal cord (C6) or dorsal root (C3-6) transection in the intact and decerebellated vagotomized cat. Respiratory timing (inspiratory and expiratory duration) was determined from the EMGdi record, and the peak integrated EMGdi (fEMGdi) response was used as an index of respiratory motor drive. Our results showed that 1) cold blockade at the dorsal C6 level in an intact preparation significantly increased the peak of the fEMGdi response to TO and was reversible upon rewarming; 2) as previously reported, decerebellation coupled with bilateral vagotomy significantly decreased the peak fEMGdi response to TO with no effect on timing; 3) cold blockade (- 1°C) of the dorsal cord at C6 significantly attenuated this inhibition and subsequent dorsal rhizotomy at C3-6 completely abolished thus inhibition; and 4) decerebellation, cold blockade of the dorsal cord (C6), and dorsal rhizotomy (C3-6) did not significantly affect baseline values in bilaterally vagotomized cats. It is concluded that spinal afferents arising from respiratory muscles can play a role in modulating the respiratory response to added mechanical loads. Cerebellar activity can modulate or mask the influence of respiratory muscle afferents.

Original languageEnglish
Pages (from-to)682-687
Number of pages6
JournalJournal of Applied Physiology
Volume75
Issue number2
DOIs
StatePublished - 1993

Keywords

  • cerebellum
  • cold blockade
  • diaphragm
  • dorsal column
  • intercostal
  • vagus

ASJC Scopus subject areas

  • General Medicine

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