Intrapulmonary chemoreceptor control of ventilatory movements in the self-ventilating chicken

The importance of intrapulmonary chemoreceptors (IPC), sensitive to PCO2 in the lung, in the control of ventilatory movements is yet to be demonstrated in the self-ventilating bird. We distinguished between the effects of PCO2 on IPC and on extrapulmonary CO2-sensitive receptors (EPC) in anaesthetized cockerels by denervating IPC in the right lung, ligating the left pulmonary artery and changing PICO2. Left IPC were thus exposed to a combination of PCO2 from inspired gas and dead space, while EPC were exposed to greatly increased arterial PCO2 resulting from the ventilation-perfusion inequality. At 0 Torr PICO2, steady state ventilatory depth and frequency did not change (P greater than 0.5) after the ligation, although PaCO2 rose by 12.2 +/- 1.7 Torr. After the ligation, ventilatory movements were more sensitive to increasing PICO2. Tracheostomy, which results in a greater decrease in PCO2 in the innervated lung after ligation, produced greater effects. We conclude that these responses were due to the strong controlling influence of IPC on ventilatory movements in the self-ventilating cockerel.