Vascular responsiveness of rabbit common carotid, renal and femoral arteries to alpha-adrenoceptor agonists.
The stainless steel cannula inserting method was used to observe vascular effects of alpha-adrenoceptor agonists, phenylephrine (PE), methoxamine (ME), clonidine (CL) and xylazine (XY), on the isolated, perfused rabbit common carotid, renal and femoral arteries. PE and ME induced a dose-dependent vasoconstriction that was readily suppressed by treatment with bunazosin, an alpha 1-adrenoceptor blocker. CL induced a constriction only in common carotid arteries, and this was readily suppressed by bunazosin. In preparations preconstricted by phenylephrine, CL and XY dose-dependently induced vasodilations in the 3 types of arteries, and these vasodilations were not modified by a potent alpha 2-adrenoceptor antagonist, midaglizole. In preparations preconstricted by prostaglandin F2 alpha, CL and and XY did not produce any significant vasodilation, but CL induced a vasoconstriction in common carotid arteries that was completely blocked by bunazosin. Thus, it is concluded that: 1) alpha 1-adrenoceptors are functionally predominant in rabbit peripheral arteries, 2) the alpha 2-adrenoceptor agonist-induced vasodilation may be due to an antagonistic action towards alpha 1-mediated constrictions, and 3) clonidine has alpha 1-adrenoceptor stimulating properties in rabbit common carotid artery but not in renal and femoral arteries.
Fujiwara
T
T
Department of Pharmacology, Shinshu University School of Medicine, Matsumoto, Japan.
Chiba
S
S
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D002339:Carotid Arteries / Q000187:drug effects*; D015237:Dinoprost / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D005263:Femoral Artery / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology; D011817:Rabbits; D012077:Renal Artery / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011799:Quinazolines; D010656:Phenylephrine; C018176:bunazosin; D015237:Dinoprost