Endothelin action on cerebral circulation in unanesthetized goats.
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.
García
J L
JL
Departamento de Fisiología, Facultad de Medicina, Universidad Autónoma, Madrid, Spain.
Gómez
B
B
Monge
L
L
García-Villalón
A L
AL
Diéguez
G
G
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002342:Carotid Artery, External / Q000502:physiology; D002536:Cerebral Arteries / Q000187:drug effects / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D016232:Endothelins / Q000494:pharmacology*; D005260:Female; D006041:Goats; D006339:Heart Rate / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D012016:Reference Values; D014655:Vascular Resistance / Q000187:drug effects
D016232:Endothelins