Discharge of intrapulmonary chemoreceptors and its modulation by rapid F1CO2 changes in decerebrate ducks.

Single-unit activity was recorded from intrapulmonary chemoreceptors (IPC) in decerebrate ducks inspiring room air (fresh air or control breath), or a short pulse of room air preceded and followed by 5% CO2 (fresh air pulse or experimental breath). Of 36 IPC studied, 28 fired a burst of impulses of similar duration to the fresh air pulse; delaying the fresh air pulse until later and later in inspiration progressively delayed the IPC burst. The remaining 8 IPC did not respond discretely to the fresh air pulse, rather their discharge was reduced diffusely in one or both of the ventilatory phases. The average discharge of the IPC population had a cyclic character during control breathing, with peak discharge mid-way through inspiration and essentially a constant discharge during expiration. An experimental breath had a similar IPC discharge pattern but peak inspiratory discharge was reduced; delaying the fresh air pulse delayed the population IPC burst. The results indicate that IPC could mediate the previously reported changes in T1 and TE that occur when the timing of a fresh air pulse is manipulated in conscious chickens [(Tallman et al. (1979). Am. J. Physiol. 237: R260-R265)].