We quantified the neural discharge of intrapulmonary chemoreceptors (IPC) innervating the left lungs of anesthetized Pekin ducks. Right and left lungs were separately unidirectionally ventilated. Alternating steps in CO2 concentration (0-6%, 11-s period) were delivered to the left lung under control conditions [mixed venous PCO2, (Pv̄(CO2)) 43 ± 4 Torr] and under venous CO2 load conditions (Pv̄(CO2) 79 ± 6 Torr). During venous CO2 loading the right lung was ventilated with 10-20% CO2, while the left lung was ventilated with a sufficient flow of gas containing 0% CO2 to maintain normal expired PCO2 (indicated by constant IPC discharge rate). Venous loading increased the peak-to-peak amplitude of the oscillation in IPC discharge by 4.3 ± 1.8 s-1 (n = 11, P < 0.05), left lung ventilation was increased 2.6-fold, and the IPC step response became more prompt. The mean IPC discharge rate during the CO2 stepping cycle was not significantly affected (11.8 ± 1.4 during control vs. 10.3 ± 1.3 s-1 during venous loading). Increased IPC discharge oscillations were due to enhancement of the dynamic overshoot in receptor discharge after the 6-0% downstep in inspired CO2 and to a depression of discharge during 6% inspired CO2. We propose that the phasic enhancement of IPC discharge oscillations during venous CO2 loading may cause feedback inhibition of ventilatory drive.
|Original language||English (US)|
|Journal||American Journal of Physiology - Regulatory Integrative and Comparative Physiology|
|Issue number||1 35-1|
|State||Published - Jan 1 1994|
- respiratory control
ASJC Scopus subject areas
- Physiology (medical)