Avian arterial chemoreceptor responses to steps of CO₂ and O₂

The responses of avian arterial chemoreceptor preparations to 44-sec steps of inspired CO₂ and O₂ were quantified. Anesthetized ducks were unidirectionally ventilated, arterial pH was recorded with a fast responding indwelling electrode, and neural activity was recorded from 28 preparations consisting of dissected filaments of the vagus nerve (23 single-fibered, 5 few-fibered). We analyzed responses using cycle-triggered stimulus histograms of neural discharge, cross correlation analysis, and analysis of variance. Average responses of the chemoreceptor preparations to Pa_CO2 steps from 24 ± 1 to 38 ± 1 Torr were larger (per 56 ± 2 Torr. Average responses to CO₂ steps usually appeared more rate sensitive when measured during arterial hypoxia than during arterial normoxia. These characteristics are very much like those reported for mammalian arterial chemoreceptors, except that responses of avian chemoreceptor preparations to repetitive CO₂ steps were highly variable according to statistical analysis.