Iturriaga, Rodrigo, and Julio Alcayaga. Effects of CO₂- 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 (CA) and frequency of chemosensory discharges (f_x) from superfused cat carotid body: 1) the addition of CO₂- 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 (PO₂ h  40 Torr) with and without CO₂-; and 4) the impact of several boluses of dopamine (DA; 10-100 µg) on hypoxic and hypercapnic challenges. With CO₂-, hypoxia increased f_x which preceded CA increases, whereas hypercapnia raised f_x but did not consistently increase CA. Repeated stimuli induced similar f_x increases, but attenuated CA. After DA, hypoxia produced larger CA, which preceded chemosensory responses. Without CO₂-, hypoxia produced a similar pattern of CA and f_x responses. Switching to Tyrode solution with CO₂- at pH 7.40 raised f_x but did not increase CA. With CO₂- and after DA, hypoxic-induced CAs were larger than in its absence. Results suggest that DA release is not essential for chemosensory excitation.