Interaction of dopamine and haloperidol with O2 and CO2 chemoreception in carotid body

Abstract

Effects of dopamine and of a dopaminerigc blocker, haloperidol, on the responses of carotid body chemoreceptors to hypoxia and hypercapnia were investigated in 16 anesthetized cats. I.v. infusion of dopamine (10-20 .mu.g/min) decreased carotid body chemoreceptor responses to hypoxia and hypercapnia. The effect was greater at higher levels of arterial O2 and CO2 tension (PaO2 and PaCO2) stimulus. The magnitude of the dopamine effect depended on the degree of both PO2- and PCO2-mediated excitation of the receptors. Haloperidol potentiated responses to both hypoxia and hypercapnia but apparently did not stimulate the receptors in the absence of the stimuli. Potentiation by haloperidol and inhibition by dopamine of excitatory effects due to PaO2. decrease and PaCO2 increase are complementary. Chemoreception of dopamine, O2 and CO2 may converge at some site in the carotid body. Persistence of hypoxic and hypercapnic responses, following dopamine-blocking doses of haloperidol, does not support the theory that regulation of dopamine release is responsible for O2 and CO2 chemoreception in carotid body of the cat.