Journal of Applied Physiology, Vol 48, Issue 2 320-328, Copyright © 1980 by American Physiological Society
Spontaneous mechanical activities of dog trachealis muscle in vivo
W. H. Beinfield and J. Seifter
Isometric strain gauge arches attached transversely and longitudinally to
cervical trachealis muscle (CTM) recorded spontaneous mechanical activities
(SMA), passive constriction, and longitudinal tension in 64 dogs
anesthetized with pentobarbital. Inspiratory tracheal elongation increased
longitudinal tension and passively constricted CTM. Occasional overlapping
of tracheal cartilages observed on initial exposure of cervical trachea
appeared to be due to unprovoked persistent increases in SMA. Three major
types of rhythmic SMA oscillations occurred in 42 lightly anesthetized
dogs: slow oscillations 50 - 200 s/cycle (19 dogs); sinelike waves 20-30
s/cycle (12 dogs); and sinelike waves superimposed on slow oscillations (11
dogs). These rhythms were dampened by pharmacologically induced incrases or
decreases in SMA. They disappeared following deeper anesthesia,
atropinization, or bilateral vagotomy. Intravenous acetylcholine increased
while isoproterenol decreased SMA before and after bilateral vagotomy in
spontaneously breathing dogs as well as in artificially ventilated
curarized dogs whose tracheas were isolated in situ. Atropine blocked
acetylcholine actions and propranolol blocked those of isoproterenol.
Changes in SMA induced pharmacologically did not correlate with
simulatenous alterations in systemic arterial pressure of ventilatory
patterns.
