Pharmacological features of vascular responses of isolated rat common carotid arteries to vasoactive substances revealed by the cannula inserting method.

Using the cannula inserting method, we studied vascular responses of isolated rat common carotid arteries to 15 vasoactive substances. Intraluminal injections of phenylephrine, norepinephrine (NE), angiotensin II, 5-hydroxytryptamine (5-HT) and prostaglandin F2 alpha (PGF2 alpha) induced a strong vasoconstriction in such a way that a maximum increase in perfusion pressure amounted to approximately 50 mmHg. The order of their potencies were as follows: Phenylephrine greater than or equal to NE greater than or equal to angiotensin II greater than PGF2 alpha greater than or equal to 5-HT much greater than KCl. The selective alpha-2 agonists, xylazine and clonidine, induced nor or a slight vasoconstriction. Tyramine, ATP and acetaldehyde induced only a slight constriction. Histamine, adenosine and acetylcholine (ACh) induced no effect. In preparations preconstricted by a high dose of NE, ACh and isoproterenol induced a vasodilation in a dose-related manner. It is concluded that the cannula inserting method is useful for investigating vascular responses in isolated and perfused rat vessels.