Mechanisms underlying post-inspiratory depolarization in post-inspiratory neurons of the cat

The mechanism of the post-inspiratory depolarization in bulbar post-inspiratory neurons was investigated in decerebrate cats with a coaxial multibarrelled microelectrode technique. Iontophoresed tetrodotoxin eliminated a dominant part of the post-inspiratory depolarization and left a small depolarization to occur. This residual potential was increased with depolarization. When depolarization exceeded a potential of average -63 mV, there appeared a large bell-shaped depolarization that was suppressed by iontophoresed cadmium. These results suggest that the post-inspiratory depolarization in this neuron is formed by the cooperation between excitatory synaptic potentials and voltage-dependent Ca2+ currents.