Intracellular recordings of respiratory neurons in the lateral medulla of piglets.

Membrane potentials of respiratory neurons in the ventral respiratory group were recorded using intracellular techniques in the medulla of newborn piglets. Three types of neurons were demonstrated: inspiratory neurons with an augmenting pattern of spike activity during inspiration; postinspiratory neurons with a short decrementing firing pattern that started immediately after inspiration ended; and stage II expiratory neurons with an augmenting spiking pattern that began shortly after inspiratory termination and ended before onset of the next inspiration. When not firing, the membrane potential trajectories of each cell type revealed two complementary patterns of relative inhibition. This latter finding suggests arrival of inhibitory synaptic potentials during these periods. These findings suggest that the respiratory control mechanisms of the newborn piglet are organized in a three-phased manner similar to that of adult cats.