Journal of Applied Physiology, Vol 53, Issue 1 21-29, Copyright © 1982 by American Physiological Society
Sympathetic inhibition of histamine-induced contraction of canine trachealis in vivo
A. R. Leff, N. M. Munoz and S. G. Hendrix
The effect of sympathetic stimulation on histamine-induced tracheal
contraction was studied in 42 dogs in situ. After cholinergic blockade with
atropine, dose-response curves to intra-arterial (ia) histamine
(10(-10)-10(-6) mol) were performed in 11 adrenal-intact (ADi) and 5
adrenalectomized (ADx) dogs receiving steady-state sympathetic stimulation
from continuous intravenous infusion (62.5-312 micrograms . kg-1 . min-1)
of 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP). In ADi dogs receiving
maximal sympathetic prestimulation (312 micrograms . kg-1 . min-1 DMPP),
tracheal tension barely exceeded base-line resting tension after 10(-6) mol
ia histamine. In five dogs, tracheal tension after maximal sympathetic
prestimulation exceeded base line for greater than or equal to 10(-8) mol
ia histamine. In 12 other dogs, reversal of histamine-induced contraction
by maximal sympathetic prestimulation was studied. Tracheal tension
decreased 45.6 +/- 4.4 g/cm in four ADi dogs (P less than 0.001), 12.4 +/-
2.8 g/cm in four ADx dogs (P less than 0.02), and 2.2 +/- 2.5 g/cm in four
control dogs receiving sham infusions (P greater than 0.90). No evidence
was found for nonadrenergic relaxation of canine airway smooth muscle. We
conclude that tracheal sympathetic nerves cause significant antagonism of
histamine-induced contraction, which is augmented by adrenal secretion. We
also report a pharmacological method for dose-related steady-state
sympathetic stimulation of canine airways.
