Differential effects of oligomycin on carotid chemoreceptor responses to O₂ and CO₂ in the cat

Effects of oligomycin on carotid chemoreceptor responses to O₂ and CO₂ were investigated using an in situ perfusion technique. Cats were anesthetized, paralyzed, and artificially ventilated. To avoid a possible reaction between an oligomycin-ethanol mixture and blood, we administered oligomycin to the carotid body via cell- and protein-free perfusate. Except for the perfusion periods, the carotid body received its own natural blood supply. Responses to O₂, CO₂, sodium cyanide, and nicotine of the same carotid chemoreceptor afferents were studied before and after each perfusion. An appropriate low dose of oligomycin completely blocked carotid chemoreceptor response to O₂ while preserving the CO₂ response. At the same time cyanide response was attenuated leaving nicotine response intact. Additional doses of oligomycin attenuated carotid chemoreceptor response to CO₂ as well. Perfusion with a blank solution containing ethanol did not change the carotid body chemoreceptor responses. These effects of oligomycin on carotid chemoreceptor responses to O₂ and CO₂ were reversible, and restoration of the response to CO₂ preceded that to O₂. In addition, oligomycin administered into the blood with close intra-arterial injection produced similar differential blockade of O₂ and CO₂ chemoreception, preserving the nicotine and dopamine effects. This study confirmed the previous findings and provided new evidence showing that 1) the responses of carotid chemoreceptor to O₂ and CO₂ were separable by oligomycin due to the inhibition of oxidative phosphorylation and 2) the responses to nicotine and dopamine were intact even after blockade of O₂ response.