Effects of diltiazem on the TEA-induced plateau of nodose ganglion action potentials.

The effects of diltiazem, a Ca2+-antagonist, on the tetraethylammonium (TEA)-induced plateau of the action potentials of nodose ganglia in the rabbit were investigated with intracellular recording techniques. TEA (10mM) formed a long lasting plateau in the falling phase of action potentials when applied in the superfusion solution. Membrane conductance during the plateau was increased and both duration and amplitude of the plateau were Ca2+-dependent. Hyperpolarizing test pulses terminated this TEA-induced plateau whereas depolarizing pulses prolonged it. Diltiazem depressed this TEA-induced plateau dose-dependently (I50 value, 8.6 X 10(-7) M). The present results provide evidence that plateau is elicited by the activation of a voltage-dependent Ca2+-influx and suggest that the TEA-induced plateau could be a useful tool to investigate the inward Ca2+-current in the neuron.