Separation of carotid body chemoreceptor responses to O2 and CO2 by oligomycin and by antimycin A.

The cat carotid chemoreceptor O2 and CO2 responses can be separated by oligomycin and by antimycin A. Both of these agents greatly diminish or abolish the chemoreceptor O2 response but not the nicotine or CO2 responses. After either oligomycin or antimycin, the responses to increases and decreases in arterial CO2 partial pressure (PaCO2) consisted of increases and decreases in activity characterized respectively by exaggerated overshoots and undershoots. These were eliminated by the carbonic anhydrase inhibitor, acetazolamide, suggesting that they resulted from changes in carotid body tissue pH. The steady-state PaCO2 response remaining after oligomycin was no longer dependent on arterial O2 partial pressure (PaO2). All effects of antimycin were readily reversible in about 20 min. The separation of the responses to O2 and CO2 indicates that there may be at least partially separate pathways of chemoreception for these two stimuli. The similarity of the oligomycin and antimycin results supports the metabolic hypothesis of chemoreception.