Journal of Applied Physiology, Vol 43, Issue 4 643-647, Copyright © 1977 by American Physiological Society
Bronchial reactivity: interaction between vagal stimulation and inhaled histamine
M. K. Benson and P. D. Graf
The interaction between the effects of vagal stimulation and inhaled
histamine on the bronchi was studied in anesthetized dogs. Reactivity was
assessed by measuring changes in bronchial caliber visualized with tantalum
bronchograms. In seven vagotomized dogs the bronchoconstrictor response to
a combination of electrical stimulation of the vagus nerves and inhaled
histamine solution produced a mean reduction in airway diameter (Daw) of
2.21 mm which was significantly greater than the additive results of the
two stimuli applied separately (mean decrease in Daw 0.29 +/- 0.91 mm). In
three dogs the effect of vagal stimulation was to produce a shift in the
dose-response curve to inhaled histamine. These results indicate that the
effect of the base-line bronchomotor tone must be considered in the
evaluation of the effect of vagal blockade on airway reactivity. An
increase in the resting degree of bronchomotor tone may contribute to the
hyperreactivity observed in patients with asthma.
