Effect of temperature on the CO2 sensitivity of avian intrapulmonary chemoreceptors.

We determined linear regressions of discharge frequency on ln PCO2 of 23 intrapulmonary chemoreceptors (IPC) from eight hyperthermic, adult cockerels. At low PCO2, IPC in hyperthermic cockerels discharged slower than IPC measured in euthermic cockerels; above 25 torr PCO2, however, they discharged faster than euthermic IPC. Thus, IPC were less sensitive to PCO2 during hyperthermia. We calculate that a 1 degree C increase in the temperature of the lung (TL) causes the slope of the linear regression of discharge frequency on ln PCO2 to be less negative by 1.5 +/- 0.5 imp (sec X ln PCO2)-1 and that, for any increase in TL above normal (41.5 degrees C), the average IPC discharge frequency equals (-10.7 + 1.5 (TL -41.5] X (ln (PCO2/25.0] + 3.7. This relationship may be partly responsible for the increased tidal volume and decreased respiratory frequency observed when body temperature increases during constant PaCO2.