Response of canine internal carotid system to acetylcholine.
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.
Diéguez
G
G
Departamento de Fisiología, Facultad de Medicina, Universidad Autónoma, Madrid, Spain.
Nava-Hernández
E
E
Valle
J
J
García-Villalón
A L
AL
García
J L
JL
Monge
L
L
Gómez
B
B
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002339:Carotid Arteries / Q000187:drug effects / Q000502:physiology*; D002342:Carotid Artery, External / Q000187:drug effects / Q000502:physiology; D002343:Carotid Artery, Internal / Q000187:drug effects / Q000502:physiology; D002536:Cerebral Arteries / Q000187:drug effects / Q000502:physiology*; D004285:Dogs; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology
D000109:Acetylcholine