Journal of Applied Physiology, Vol 54, Issue 1 134-139, Copyright © 1983 by American Physiological Society
Intravenous versus inhaled atropine for inhibiting bronchoconstrictor responses in dogs
M. J. Holtzman, M. P. McNamara, D. Sheppard, L. M. Fabbri, H. L. Hahn, P. D. Graf and J. A. Nadel
We studied whether the muscarinic antagonist, atropine, given intravenously
or by inhalation, inhibits the bronchoconstrictor responses to inhaled
acetylcholine and to acetylcholine released by electrical stimulation of
the vagus nerves to the same degree. We assessed bronchoconstrictor
responses in anesthetized dogs by determining the increase in total
pulmonary resistance before and after increasing doses of atropine and then
constructing inhibition dose-response curves. Before atropine the responses
to the two stimuli were equal in magnitude. After intravenous atropine
(initial dose 0.12 micrograms/kg, total dose 16 micrograms/kg) both
responses were progressively inhibited to a similar degree. By contrast,
after inhaled atropine (initial dose 0.02 micrograms/kg, total dose 2.4
micrograms/kg) the response to acetylcholine inhalation was inhibited to a
much greater degree than the response to vagal stimulation. Thus, in
studies designed to inhibit bronchoconstriction due to an inhaled
muscarinic agonist to the same degree as bronchoconstriction due to a vagal
reflex, atropine might better be given intravenously than by inhalation.
