AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 3 581-R587, Copyright © 1991 by American Physiological Society
Endothelin action on cerebral circulation in unanesthetized goats
J. L. Garcia, B. Gomez, L. Monge, A. L. Garcia-Villalon and G. Dieguez
Departamento de Fisiologia, Facultad de Medicina, Universidad Autonoma, Madrid, Spain.
The effects of endothelin 1 on the internal maxillary artery blood flow,
measured as an index of cerebral blood flow, were examined in six
unanesthetized goats under control conditions, hypercapnia induced by
inhalation of 10% CO2 in air, hypertension by intravenous infusion of
norepinephrine, and hypotension by intravenous injection of diazoxide.
Under control, administration of endothelin (0.01-0.3 nmol) into the
internal maxillary artery produced dose-dependent sustained decreases in
cerebral blood flow and increases in cerebrovascular resistance; higher
doses (0.1 and 0.3 nmol) also caused hypertension and bradycardia. During
hypercapnia or hypertension, endothelin did not significantly affect
cerebral blood flow, and only higher doses (0.1 and/or 0.3 nmol) increased
cerebrovascular resistance, but this was lower than under control. However,
under hypotension endothelin evoked a higher reduction in cerebral blood
flow and increment in cerebrovascular resistance, and systemic effects were
also more marked than under control. Therefore endothelin is a potent
cerebral vasoconstrictor, and this effect is very attenuated during
hypercapnia and hypertension but is increased under hypotension.
