Two modes of respiratory rhythm generation in the newborn rat brainstem-spinal cord preparation.

Two respiration-related rhythm generators, the pre-Bötzinger complex inspiratory and the parafacial pre-inspiratory rhythm generators, have been identified in the medulla of rodents that produce intrinsic periodic bursts. Although both generators can be independently active under specific conditions, they interact as a coupled oscillator system to regulate the respiratory rhythm. Here, we summarize different mechanisms of modulation of the respiratory rhythm in the brainstem-spinal cord preparation of newborn rats and discuss factors determining rhythm generator dominance. We show two different modes of respiratory rhythm generation in the brainstem-spinal cord preparation that depends on the background stimulation level.