The effect of calcium channel blockers on alpha 1- and alpha 2-adrenoceptor-mediated vascular responsiveness in man.
This study investigated the effects in normotensive males of the calcium channel blockers, verapamil and nisoldipine, on the pressor responses mediated via alpha-adrenergic and non-adrenergic mechanisms. After the first doses of each drug and after 4 days continued treatment both verapamil and nisoldipine significantly attenuated the responses to angiotensin II with three- to fivefold rightward shifts of the pressor dose-response curves. Rightward shifts of comparable magnitude were obtained for phenylephrine (selective alpha 1-agonist), but with alpha-methylnoradrenaline (preferential alpha 2-agonist) only nisoldipine caused a significant twofold rightward shift and only during continued treatment. This study demonstrated that peripheral vascular adrenergic responses mediated via both alpha 1- and alpha 2-adrenoceptors in man are affected by calcium channel blocking drugs. There was no evidence that this effect was specifically linked to the alpha 2-adrenoceptor. The functional antagonism of peripheral vasopressor mechanisms was not significantly different for verapamil and nisoldipine.
Elliott
H L
HL
University Department of Materia Medica, Stobhill General Hospital, Glasgow, UK.
Pasanisi
F
F
Sumner
D J
DJ
Reid
J L
JL
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D008297:Male; D015737:Nisoldipine / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D011942:Receptors, Adrenergic, alpha; D015737:Nisoldipine; D014700:Verapamil