Carbon dioxide sensitivity of aortic chemoreceptors in the cat

Steady state CO2 sensitivity in the aortic chemoreceptors was variable. For 70.3% of the steady state response lines to increasing CO2 the slope was not significantly different from zero. For 24.3%, it was significantly positive and for 5.4% significantly negative. In contrast, in 86.7% of cases the oscillating response to alternate breaths of high and low CO2 suggested a transient response line which was significantly steeper than the steady state line. Removing CO2 from a high CO2 content inspirate for one breath caused a distinct drop in discharge on 83.3% of occasions. The significance of such transient CO2 sensitivity in the absence of clear steady state sensitivity is discussed.