Journal of Applied Physiology, Vol 49, Issue 6 1010-1015, Copyright © 1980 by American Physiological Society
Evidence for alpha-adrenergic innervation of the isolated canine thoracic duct
J. A. Russell, K. Zimmerman and W. F. Middendorf
The excitatory innervation of isolated thoracic duct segments was studied
using tissue bath techniques. No spontaneous activity was present in
longitudinal or helical strips obtained from a portion of the thoracic duct
cephalad to the hilum of the lung. Norepinephrine (10(-8) to 10(-5) M) and
tyramine (3 x 10(-5) M) produced contractions that were antagonized by
phentolamine (2 x 10(-5) M) and phenoxybenzamine (10(-7) M). Acetylcholine
(10(-7) to 10(-4) M) produced contractions that were antagonized by
atropine (5 x 10(-9) M). Thoracic duct strips also contracted in response
to field electrical stimulation, and maximal responses were obtained with a
stimulus of 15 V, 15 Hz, and 1-ms pulse duration. These electrically
induced contractions were abolished by tetrodotoxin (5 x 10(-7) M),
phentolamine (2 x 10(-5) M), phenoxybenzamine (10(-7) M), and guanethidine
(3 x 10(-6) M), but not by atropine (10(-6) M). We conclude that smooth
muscle of the canine thoracic duct contains alpha-adrenergic and
acetylcholine receptors, both of which cause contraction when stimulated.
However, only the alpha-receptors appear to be innervated.
