Effects of thoracic dorsal rhizotomy or vagotomy on inspiratory muscle activity at various levels of chemical drive

Edgardo D'Angelo, Marco Schieppati

Research output: Contribution to journalArticlepeer-review

Abstract

The relationship between relative peak activity (moving average EMG) of the diaphragm (Adi) and of the cranial (2nd and 3rd) external intercostal or parasternal muscles (Aic) was assessed during rebreathing in animals before and after bilateral thoracic (T1-T4) dorsal rhizotomy (TDR) and/or bilateral vagotomy (VGT). The relationship had the form Aic = a Adib under all conditions. In intact rabbits and cats mean values for b were 1.48 and 1.79, respectively, a being unity by definition. Neither TDR nor VGT changed b;a decreased to about 0.15 with TDR and halved with VGT only if performed before TDR. Selective reflex facilitation of inspiratory intercostals with occlusions at FRC was observed after VGT and was abolished by TDR. Neither VGT nor TDR affected Adi time course. Hence: (1) central command to α-motoneurones of the major inspiratory muscles differs; (2) proprioceptive feedback markedly increases external intercostal activity, apparently by multiplying Aic due to central command to α-motoneurones by a factor independent of chemical drive; (3) vagally mediated augmentation of Aic depends entirely on intact proprioceptive feedback. The possible role of fusimotor drive is discussed.

Original languageEnglish
Pages (from-to)221-238
Number of pages18
JournalRespiration Physiology
Volume50
Issue number2
DOIs
Publication statusPublished - 1982

Keywords

  • Diaphragm activity
  • Inspiratory intercostal activity
  • Inspiratory load
  • Intercostal reflex facilitation
  • Rebreathing
  • α-γ linkage

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine

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