Measurements of potassium changes in the cat carotid body under hypoxia and hypercapnia

With the aid of potassium-sensitive microelectrodes reinforced by bitumen (tip diameter, 1.5 micrometer), extracellular potassium activity ([K+]e) and DC potential were measured in the cat's carotid body. Under normoxic and normocapnic conditions, potassium values of 1--16 mM (mean value 7.2 mM, standard deviation 3.8 mM) and DC potential values of -11 mV to + 13 mV were recorded. With hypoxia, [K+5e increased by between 1 mM and 9 mM; DC potential was reduced by between 0.5 and 3 mV. With hypercapnia, [K+]e decreased by between 1 mM and 5 mM changes in DC potential were variable. The results suggest that, during hypoxia potassium influences the nervous structures in the carotid body whereas this influence is absent during hypercapnia.