Intrapulmonary receptor response to changes in airway-gas composition in Gallus domesticus

TLDR: A unidirectional, artificial ventilating system was used to observe respiratory and neural responses to changes in CO2 concentration in pulmonary airways of the chicken.

Abstract: 1 A unidirectional, artificial ventilating system was used to observe respiratory and neural responses to changes in CO2 concentration in pulmonary airways of the chicken 2 Sectioning any of the three pulmonary branches of the vagus slowed the respiratory response to sudden removal of CO2 from unidirectional ventilating gas stream 3 The impulse frequency of CO2-sensitive units was inversely related to the CO2 content in the ventilating gas stream 4 Abrupt elimination of CO2 from the ventilatory gas stream caused a transient burst of activity from CO2-sensitive receptors, which quickly adapted to a constant discharge frequency Fifty percent of the units responded within 0·35 sec after CO2-free gas reached the lungs The neural response to abrupt re-addition of CO2 to the gas stream was less rapid 5 Acetylcholine or NaCN injected into the pulmonary artery had no apparent effect on the discharge of CO2-sensitive receptors Veratridine temporarily reduced discharge and occasionally produced short, rapid bursts of activity 6 Hypoxia and hyperoxia (5% and 80% O2) produced no significant change in the discharge of CO2-sensitive receptors 7 Carbon dioxide-sensitive units in spontaneously breathing chickens were silenced by adding 10% CO2 to the inspired gas; the units responded vigorously to inflation of the respiratory system with a gas containing no CO2 but remained silent during inflation with gas containing 15% CO2 Units insensitive to CO2, which increased their impulse frequency during inflation regardless of the CO2 content of the inflating gas, also were observed