Effects of CO2- HCO 3 − on catecholamine efflux from cat carotid body

Abstract

Iturriaga, Rodrigo, and Julio Alcayaga. Effects of CO2-[Formula: see text]on catecholamine efflux from cat carotid body. J. Appl. Physiol. 84(1): 60–68, 1998.—Using a chronoamperometric technique with carbon-fiber microelectrodes and neural recordings, we simultaneously measured the effects of the following procedures on catecholamine efflux (ΔCA) and frequency of chemosensory discharges ( fx ) from superfused cat carotid body: 1) the addition of CO2-[Formula: see text]to Tyrode solution previously buffered with N-2-hydroxyethylpiperazine- N′ -2-ethanesulfonic acid, maintaining pH at 7.40; 2) hypercapnia (10% CO2, pH 7.10); 3) hypoxia ([Formula: see text] h ≈ 40 Torr) with and without CO2-[Formula: see text]; and 4) the impact of several boluses of dopamine (DA; 10–100 μg) on hypoxic and hypercapnic challenges. With CO2-[Formula: see text], hypoxia increased fx which preceded ΔCA increases, whereas hypercapnia raised fx but did not consistently increase ΔCA. Repeated stimuli induced similar fx increases, but attenuated ΔCA. After DA, hypoxia produced larger ΔCA, which preceded chemosensory responses. Without CO2-[Formula: see text], hypoxia produced a similar pattern of ΔCA and fx responses. Switching to Tyrode solution with CO2-[Formula: see text]at pH 7.40 raised fx but did not increase ΔCA. With CO2-[Formula: see text]and after DA, hypoxic-induced ΔCAs were larger than in its absence. Results suggest that DA release is not essential for chemosensory excitation.