Intracellular calcium response of newborn and mature glomus cells to hypoxia and KCl in the absence and presence of charybdotoxin. A: Example of an intracellular calcium experiment on glomus cells from 0-1 day old rats. Each line reflects intracellular calcium of a single glomus cell, estimated from the 340/380 nM FURA-2 ratio. B: Averaged peak [Ca2+]i response to three hypoxia challenges in sham and charybdotoxin experiments at 0-1 day. Charybdotoxin caused a slight, but significant, increase in the response to hypoxia. C: Example of an intracellular calcium experiment on glomus cells from ~14 day old rats. Each line reflects intracellular calcium of a single glomus cell. D: Averaged peak [Ca2+]i response to three hypoxia challenges in sham and charybdotoxin experiments at 14-16 day. As with the immature, charybdotoxin caused a slight, but significant, increase in the response to hypoxia.