Role of vagal afferents in the control of abdominal expiratory muscle activity in the dog

S. B. Hollstien, M. L. Carl, Edward S Schelegle, J. F. Green

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

We examined the contribution of afferent vagal A- and C-fibers on abdominal expiratory muscle activity (EMA). In seven spontaneously breathing supine dogs anesthetized with α-chloralose we recorded the electromyogram of the external oblique muscle at various vagal temperatures before and after the induction of a pneumothorax. When myelinated fibers were blocked selectively by cooling the vagus nerves to 7°C, EMA decreased to 40% of control (EMA at 39°C). With further cooling to 0°C, removing afferent vagal C-fiber activity, EMA returned to 72% of control. On rewarming the vagus nerves to 39°C, we then induced a pneumothorax (27 ml/kg) that eliminated the EMA in all the dogs studied. Cooling the vagus nerves to 7°C, during the pneumothorax, produced a slight though not significant increase in EMA. However, further cooling of the vagus nerves to 0°C caused the EMA to return vigorously to 116% of control. In three dogs, intravenous infusion of a constant incrementally increasing dose of capsaicin, a C-fiber stimulant, decreased EMA in proportion to the dose delivered. These results suggest that EMA is modulated by a balance between excitatory vagal A-fiber activity, most likely from slowly adapting pulmonary stretch receptors, and inhibitory C- fiber activity, most likely from lung C-fibers.

Original languageEnglish (US)
Pages (from-to)1795-1800
Number of pages6
JournalJournal of Applied Physiology
Volume71
Issue number5
StatePublished - 1991

Keywords

  • C-fibers
  • external oblique
  • pneumothorax
  • slowly adapting pulmonary stretch receptors
  • vagus nerve

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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