ROLE OF VAGUS NERVES IN VENTILATORY RESPONSES TO HYPERCAPNIA AND HYPOXIA IN ANAESTHETIZED AND UNANAESTHETIZED RABBITS

Minute volume/end-tidal Pco2 relationships have been determined for anaesthetized and unanaesthetized rabbits, before and after bilateral cervical vagotomy. Vagotomy depresses and flattens the upper parts of the curves (i.e., the ventilatory response to CO2 is reduced), whether the inspired CO2 mixture is in air, 100% O2 or 8-10% O2. The increase in frequency of breathing due to CO2 is especially depressed. During the maximal response to CO2 the vagotomized rabbits are able to increase ventilation in response to other stimuli. It is concluded that a lung reflex or reflexes is partly responsible for the shape of the minute volume/Pco2; curve in rabbits with intact vagi. © 1969.