Attenuation of sympathetic vasoconstriction by nifedipine: the role of vascular alpha 2-adrenoceptors.
The effects of nifedipine on hindlimb vasoconstriction caused by norepinephrine infusion and sympathetic stimulation (0.1-1.0 Hz) were compared in dogs given 0.12 mg/kg prazosin or 0.3 mg/kg rauwolscine. Constrictions due to stimulation or norephinephrine with prazosin, presumed to be mediated by vascular alpha 2-adrenoceptors, were significantly attenuated by 30 micrograms/kg nifedipine, while constrictions with rauwolscine, presumably alpha 1-mediated, remained unaffected. These data support the hypothesis that the antihypertensive effect of calcium antagonists is based upon interference with alpha 2-mediated sympathetic vasoconstriction.
D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006614:Hindlimb / Q000098:blood supply; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D012039:Regional Blood Flow / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects*
D011942:Receptors, Adrenergic, alpha; D009543:Nifedipine