AJP - Heart and Circulatory Physiology, Vol 261, Issue 5 1392-H1396, Copyright © 1991 by American Physiological Society
Response of canine internal carotid system to acetylcholine
G. Dieguez, E. Nava-Hernandez, J. Valle, A. L. Garcia-Villalon, J. L. Garcia, L. Monge and B. Gomez
Departamento de Fisiologia, Facultad de Medicina, Universidad Autonoma, Madrid, Spain.
The reactivity of the canine internal carotid system to acetylcholine
(10(-8)-10(-4) M) was studied isometrically with 4-mm cylindrical segments
from cervical and cavernous portions of the internal carotid artery and
from the middle cerebral artery. Under control conditions, the cervical
portion relaxed to every dose, the cavernous portion relaxed at low
concentrations (10(-8)-10(-6) M) and contracted at higher concentrations
(10(-5)-10(-4) M), whereas the middle cerebral artery contracted to every
dose of acetylcholine. These responses were blocked by atropine (10(-6) M).
Without endothelium, the cervical portion exhibited a lower relaxation, the
cavernous portion contracted, and the middle cerebral artery was
practically unresponsive to acetylcholine. These responses were also
blocked by atropine. It suggests that the reactivity of the internal
carotid system to acetylcholine 1) is endothelium dependent and 2) changes
as it courses toward the brain, and this could be related to different
embryological origin of the components of this arterial system.
