Figure 5.

Effects of hypoxia on catecholamine secretion from AMCs after various chronic treatments in culture. Carbon fiber amperometry was used to detect stimulus-evoked release of CATs from AMCs cultured for 7 d in the presence of nicotine (Nic) (50 μm), with or without mecamylamine (Mec) (100 μm), hexamethonium (Hex) (100 μm), and α-bungarotoxin (α-btx) (100 nm), or in the presence of the depolarizing stimulus high K⁺ (30 mm). Hypoxia stimulated quantal CAT release as indicated by an increase in event frequency (events per minute) in control AMCs and AMCs grown chronically in high K⁺. In contrast, hypoxia failed to stimulate CAT secretion from AMCs cultured in the presence of nicotine; however, this blunting effect of nicotine was prevented after coincubation with Mec or α-btx, but not hex. Data were obtained from seven cells for each treatment [the asterisk (*) indicates significant difference, p < 0.01, from normoxic (Nox) control]. Error bars indicate SEM. The top traces show sample recordings of quantal CAT release from AMCs under the conditions indicated.