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

Abstract

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 FZa (PGFZa) 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 >_ NE _> angiotensin II > PGFZa >_ 5-HT>>KCI. The selective alpha-2 agonists, xylazine and clonidine, induced no 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. cannula inserting method ; rat common carotid artery In 1983, Hongo and Chiba developed a new perfusion technique for isolated vessels, and Tsuji and Chiba (1984) modified it as a steel cannula inserting method. Using this method, vascular responsiveness to a number of vasoactive substances has been investigated, because vessel preparations perfused by use of the cannula inserting method readily give an adequate perfusion pressure, and maintain a stable perfusion pressure during the experiment for a long time at a constant temperature of 3TC. Moreover, they have other advantages ; 1) the access of drugs to the arterial smooth muscle is allowed only from the endothelial side, not from both sides of the vessel unlike the cases of ordinary arterial ring and strips, and 2) the endothelium rubbed-preparation is readily obtained by use of an intraluminal bolus injection of saponin and the vascular responses of the

Existence of Functional α1A- and α1D- but No α1B-Adrenoceptor Subtypes in Rat Common Carotid Arteries

“…We found that a bolus administration of noradrenaline and phenylephrine caused a long-lasting vasoconstrictor response (1). In the present study, we examined effects of three different a1-adrenoceptor agonists, noradrenaline, phenylephrine and methoxamine.…”

“…In the past we studied the functional characteristics of vascular responses of isolated rat common carotid arteries (1,7,8). We found that a bolus administration of noradrenaline and phenylephrine caused a long-lasting vasoconstrictor response (1).…”

“…It was demonstrated that noradrenaline and phenylephrine caused a long-lasting vasoconstriction (30 -60 min) even in a single injection of each compound, although other vasoconstrictor compounds (5-HT, PGF2=, angiotensin II or KCl) caused a relatively short-lasting constriction (within 20 min), indicating that this artery responded well to the a 1-adrenoceptor agonist. On the other hand, selective a2-adrenoceptor agonists, clonidine and xylazine, did not cause any vascular response in the same arterial preparation, indicating that there are no functional a2-adrenoceptors (1). Thus, it is interesting to clarify the a1-adrenoceptor subtypes in the rat common carotid artery.…”

Long-term Effects of UV Light on Contractility of Rat Arteries In Vivo¶

“…The cumulative dose–response curves for the receptor agonists phenylephrine (PE) (1 × 10 −9 to 1 × 10 −5 mol/L), prostaglandin F 2α (PGF 2α ) (1 × 10 −9 to 1 × 10 −5 mol/L) and serotonin (5HT) (1 × 10 −9 to 1 × 10 −5 mol/L) were then recorded for each arterial ring. These three agonists are all potent constrictors of the rat carotid artery (10). A receptor agonist applied to SMC couples with its receptors on the cellular membrane and activates the G‐proteins.…”