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.