Characteristics of 5-HT-containing chemoreceptor cells of the chicken aortic body.

1. Voltage-dependent and oxygen-sensitive currents in 5-HT-containing epithelioid cells isolated from chicken thoracic aorta were examined using the whole-cell patch clamp technique. 5-HT immunoreactive cells were identified with Neutral Red. The release of 5-HT from chicken thoracic aorta in the presence of excess KCl and veratridine was also examined using HPLC. 2. At a holding potential of -70 mV with CsCl pipette solution, depolarizing steps between -30 and +60 mV produced inward currents that were blocked by tetrodotoxin (0.2 microM). In the presence of tetrodotoxin and BaCl2 (5 mM), depolarizing steps evoked slow inward currents that were sensitive to CoCl2 (2 mM). Nifedipine (1 microM) decreased the currents to 79.4 +/- 1.7 %, and omega-conotoxin GVIA (1 microM) to 20.2 +/- 3.8 %. 3. When KCl pipette solution was used, depolarizing potentials positive to -40 mV caused outward currents that were inhibited by tetraethylammonium chloride. The K+ currents evoked by depolarizing steps to +20 mV were reduced to 90.3 +/- 0.8 % by hypoxia in five out of seven cells. Two cells failed to respond to hypoxia. The K+ current response was partly decreased by Neutral Red (20 microM). 4. Excess KCl (60 mM) and veratridine (30 microM) both caused the release of 5-HT from aortic strips. 5-HT outputs induced by both stimuli were partly inhibited by nifedipine (1 microM) and by omega-conotoxin GVIA (1 microM), and were abolished by these drugs in combination and by extracellular Ca2+ removal. 5. These results suggest that epithelioid cells containing 5-HT act as chemoreceptor cells in the chicken aortic body, having voltage-dependent Na+, K+, and L- and N-type Ca2+ channels, and oxygen-sensitive K+ channels.