Some differences in ionic and pharmacological blocking actions on the currents through Ca2+ channels in a molluscan neuron.

The inhibitory action of divalent metal cations and diltiazem, an organic Ca2+ channel blocker, on the divalent cation currents through Ca2+ channels (DCCs) was studied in a molluscan neuron using a suction pipette technique. The time course of the inhibitory action of divalent cations on the maximum peak amplitude (MPA) of DCCs was more rapid than that of diltiazem. Diltiazem equally decreased the MPA of DCCs, while the action of divalent cations varied. The action of divalent cations seemed to be dependent on their influence on membrane negative surface charge and a selectivity of Ca2+ channels, while diltiazem did not.