Intrapulmonary CO2 receptors in the duck: IV. Discharge pattern of the population during a respiratory cycle.

We used single-unit vagal recordings to study the average discharge pattern during a respiratory cycle from 57 intrapulmonary CO2 receptors in 6 ducks artificially ventilated with a Starling pump. Peak discharge frequency occurred during inspiration in 51%, expiration in 19%, and both inspiration and expiration in 30% of the receptors. Average discharge frequency from all receptors was maximum at mid-inspiration, but frequency also increased slightly during early expiration. The results suggest that the brain receives a discharge pattern from the total population of intrapulmonary CO2 receptors which is phasic with respiration. Such a signal may control the rate and amplitude of breathing.