Respiratory oscillations in discharge frequency of chemoreceptor afferents in sinus nerve and anaesthetized cats at normal and low arterial oxygen tensions.

1. The discharge of chemoreceptor afferents in preparations of the sinus nerve in spontaneously breathing anaesthetized cats has been subjected to an averaging procedure in records obtained when the animals breathed (a) air and (b) a hypoxic gas mixture. 2. The mean discharge frequency was higher in hypoxia than at normal oxygen tension. 3. Oscillations in chemoreceptor discharge frequency with the same period as respiration were obtained by the averaging procedure both at normal arterial oxygen tensions and in hypoxia, but there was no significant increase in oscillation amplitude with hypoxia. 4. The carotid body response to arterial PCO2 oscillations does not therefore appear to be amplified by hypoxia. This finding is discussed in relation to the reported dependence upon hypoxia of the ventilatory effects of tube breathing in man.