Methacholine causes reflex bronchoconstriction

Elizabeth M. Wagner, David Jacoby

Research output: Contribution to journalArticle

48 Citations (Scopus)

Abstract

To determine whether methacholine causes vagally mediated reflex constriction of airway smooth muscle, we administered methacholine to sheep either via the bronchial artery or as an aerosol via tracheostomy into the lower airways. We then measured the contraction of an isolated, in situ segment of trachealis smooth muscle and determined the effect of vagotomy on the trachealis response. Administering methacholine to the subcarinal airways via the bronchial artery (0.5-10.0 μg/ml) caused dose-dependent bronchoconstriction and contraction of the tracheal segment. At the highest methacholine concentration delivered, trachealis smooth muscle tension increased an average of 186% over baseline. Aerosolized methacholine (5-7 breaths of 100 mg/ml) increased trachealis tension by 58% and airways resistance by 183%. As the bronchial circulation in the sheep does not supply the trachea, we postulated that the trachealis contraction was caused by a reflex response to methacholine in the lower airways. Bilateral vagotomy essentially eliminated the trachealis response and the airways resistance change after lower airways challenge (either via the bronchial artery or via aerosol) with methacholine. We conclude that 1) methacholine causes a substantial reflex contraction of airway smooth muscle and 2) the assumption may not be valid that a response to methacholine in humans or experimental animals represents solely the direct effect on smooth muscle.

Original languageEnglish (US)
Pages (from-to)294-297
Number of pages4
JournalJournal of Applied Physiology
Volume86
Issue number1
StatePublished - Jan 1999
Externally publishedYes

Fingerprint

Bronchoconstriction
Methacholine Chloride
Reflex
Smooth Muscle
Bronchial Arteries
Airway Resistance
Vagotomy
Aerosols
Sheep
Muscle Tonus
Tracheostomy
Trachea
Constriction

Keywords

  • Asthma
  • Sheep
  • Trachealis muscle
  • Vagus nerves

ASJC Scopus subject areas

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

Cite this

Methacholine causes reflex bronchoconstriction. / Wagner, Elizabeth M.; Jacoby, David.

In: Journal of Applied Physiology, Vol. 86, No. 1, 01.1999, p. 294-297.

Research output: Contribution to journalArticle

Wagner, Elizabeth M. ; Jacoby, David. / Methacholine causes reflex bronchoconstriction. In: Journal of Applied Physiology. 1999 ; Vol. 86, No. 1. pp. 294-297.
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