title: [Interaction between calcium inhibitors and vascular alpha-adrenergic receptors].
abstract: A survey shall be given of the pharmacology of calcium antagonists or calcium entry blockers (CEB) in various types of cardiovascular disease. It emphasises their vasodilator potency, the common characteristic of all CEB and probably the property underlying most of their therapeutic effects apart from the antiarrhythmic activity of verapamil. All CEB relax vascular smooth muscle, particularly in arteriolar beds, thus reducing peripheral vascular resistance. Arteriolar relaxation appears to be associated with a specific inhibition of transmembrane calcium influx. Calmodulin is probably not generally involved, and neither are intracellular processes. Vasoconstriction induced by stimulation of vascular postsynaptic alpha2-adrenoceptors, using selective agonists, is reduced by CEB by a non-competitive mechanism. This interaction has been observed for different CEB like nifedipine and other dihydropyridines, verapamil and diltiazem. The effect on alpha2-adrenoceptor mediated vasoconstriction is directly associated with the calcium antagonistic potency of the drugs. On the other hand, vasoconstriction evoked by selective excitation of vascular alpha1-adrenoceptors remains virtually uninfluenced by CEB. The selective interference of CEB with alpha2-adrenoceptor stimulation. Furthermore this mechanism may contribute to the vasodilator effect of CEB, by inhibiting that part of vascular tone evoked by the stimulation of alpha2-adrenoceptors by endogenous catecholamines.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000494:pharmacology* / Q000627:therapeutic use; D002415:Cats; D006801:Humans; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D011942:Receptors, Adrenergic, alpha; D014665:Vasodilator Agents
vernacular_title: Interaction entre les inhibiteurs calciques et les récepteurs alpha-adrénergiques vasculaires.