Role of Pco2 oscillations and chemoreceptors in ventilatory response to inhaled and infused CO2.

We have previously shown in the anaesthetized rabbit that the ventilatory response to an increase in Paco2 is greater if that increase is produced by intravenous infusion of hypercapnic blood than by inhalation of CO2 (Linton et al., 1976). The present set of experiments was designed to investigate the reason for this. It was found that the difference in ventilatory response observed in the intact rabbit was abolished by cutting the carotid sinus nerves or by eliminating the pH/Paco2 oscillations in the carotid blood flow. It is concluded that the normally greater ventilatory response to intravenous infusion of hypercapnic blood compared with inhalation of CO2 is due to a respiratory signal derived from Paco2 oscillations and carried in the carotid sinus nerves.