Central respiratory drive potentials and membrane potential trajectories in phrenic motoneurons

Membrane potential trajectories were quantitatively assessed during the burst phase of cat phrenic motoneuron discharges. During burst progression the after-hyperpolarization shifted in the depolarizing direction with little change in spike threshold. Argument is made that these results constitute indirect evidence for the accumulation of potassium ions in the extracellular space of the phrenic motoneuron pool. Functional consequences regarding cell synchronization and recruitment are also discussed.