Effects of calcium antagonists on alpha-adrenoceptor mediated vasoconstrictions of the canine intermediate auricular artery.
The effects of calcium antagonists, diltiazem (DI) and verapamil (VE), on alpha-adrenoceptor-mediated contractile responses of the isolated and perfused canine intermediate auricular artery were examined by use of the stainless steel cannula inserting method. KCI (3 mg)-induced contractile responses were dose-dependently inhibited by DI and VE. Norepinephrine (0.1 microgram)-induced vasoconstrictions were also dose-dependently inhibited by both DI and VE. DI and VE shifted dose-response curves for phenylephrine and clonidine to the right with suppression of maximal responses. At large doses, DI and VE suppressed clonidine-induced contractions more than phenylephrine-induced ones, but not significantly. It is concluded that not only alpha 1- but also alpha 2-adrenoceptor mediated vasoconstrictions of the canine intermediate auricular artery are dependent on the influx of extracellular calcium ions, the present results may provide in vitro proof for the effectiveness of calcium antagonists on skin circulatory disturbances such as Raynaud's phenomenon and the isolated and perfused canine intermediate auricular artery would be a good in vitro model for investigating responsiveness of the skin supplying artery.
Ito
T
T
Department of Dermatology, Shinshu University School of Medicine, Matsumoto, Japan.
Chiba
S
S
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000294:innervation; D003000:Clonidine / Q000037:antagonists & inhibitors; D004110:Diltiazem / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000037:antagonists & inhibitors; D010656:Phenylephrine / Q000037:antagonists & inhibitors; D011189:Potassium Chloride / Q000037:antagonists & inhibitors; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D012867:Skin / Q000098:blood supply*; D014661:Vasoconstriction / Q000187:drug effects*; D014700:Verapamil / Q000494:pharmacology*
D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D011189:Potassium Chloride; D014700:Verapamil; D004110:Diltiazem; D003000:Clonidine; D009638:Norepinephrine