Evidence for initiation of calcium spikes in C-cells of the rabbit nodose ganglion.

In Na+-free solution or in tetrodotoxin (TTX, 10(-6) M) solution, direct electrical stimulation of nodose ganglion C-cells of the rabbit elicited regenerative action potentials. The amplitude of the action potentials generated in these neurons is dependent on the external Ca2+ concentration ([Ca2+]0). These action potentials were characterized by reduced amplitude, prolonged duration, and graded responses to changes of the stimulation intensity. Either removal of [Ca2+]0 or application of organic Ca2+-blocking agents, diltiazem (10(-5) M) or verapamil (10(-5) M), abolished these action potentials. The conduction of action potentials along the axon was blocked in Na+-free solution or by application of TTX. The present results provide evidence for the initiation of Ca2+-dependent action potentials in the soma membrane of mammalian nodose ganglia, and suggest that the Ca2+ ion plays an important role in the development of action potentials in the C-cell of rabbit nodose ganglia.