AJP - Heart and Circulatory Physiology, Vol 244, Issue 1 142-H149, Copyright © 1983 by American Physiological Society
Distribution of internal carotid artery blood flow in the pony
J. A. Orr, L. C. Wagerle, A. L. Kiorpes, H. W. Shirer and B. S. Friesen
This study determined whether blood flow through the internal carotid
artery (ICA) could be used to sample total cerebral blood flow in the pony.
To answer this question we considered both the anatomic arrangement of the
ICA in cadavers and the relative distribution of ICA blood flow to cerebral
and extracerebral tissue using radioactive microspheres. Acrylic corrosion
casts of the ICA indicated that this vessel traveled directly to the base
of the brain, contributing to the formation of the circle of Willis, and
did not send any significant branches to other tissues. Two vessels
(internal ethmoidal artery and internal ophthalamic artery) did arise
anteriorly from the circle of Willis and were, therefore, indirectly
supplied by the ICA. Injection of radioactive microspheres of 15 microns
diameter indicated that blood flow to extracerebral structures supplied by
the internal ethmoidal and internal ophthalamic arteries was less than 5%
of total ICA blood flow. Increases in ICA blood flow as measured with an
electromagnetic flowmeter during isocapnic hypoxia (arterial PO2 near 40
Torr) in the awake pony (n = 6) were compared with increases in total brain
flow as measured with radioactive microspheres (n = 6). ICA blood flow
increased 40% compared with a 38% increase in total brain blood flow as
measured with microspheres. We conclude that the ICA supplies predominantly
brain tissue (approximately 95%) and that changes in ICA blood flow are
representative of changes in total brain blood flow in the awake pony.
