[Calcium antagonists nicardipine and verapamil suppress Ca(2+) entry and activate Na(+) entry into platelets]

In micromolar concentrations both antagonists suppressed CA2+ entry and simultaneously elevate the agonist-induced plasma membrane depolarization due to Na+ inward current via these channels. Potentiation by nicardipine of the Na+ current induced by the platelet-activating factor, was revealed. Both antagonists caused plasma membrane depolarization suppressed by Na+ and Ca2+ ions. The depolarization disappeared after substitution of NaCl by an isotonic solution of choline chloride. The antagonists nicardipine and verapamil seem to modulate the platelet receptor-operated channels suppressing Ca2+ entry and elevating Na+ current via these channels.