Figure 7. Inhibition of the 20 pS channel conductance by extracellular Ca²⁺.

A, cell-attached patches were formed on rat glomus cells with pipette containing 100 mm CaCl₂. In physiological bath solution, no channels were activated by hypoxia or FPL64176. The current tracings shown were obtained when the pipette potential was 0 mV. No channels were present with pipette potentials ranging from −120 to +100 mV. B, cell-attached patches were formed with varying levels of Ca²⁺ in the pipette together with 140 mm KCl. FPL64176 was added to the bath solution to activate the 20 pS channel. Current tracings were obtained at pipette potential set at 0 mV. C, amplitude of the 20 pS channel plotted as a function [Ca²⁺] in the pipette. Each point is the mean ± SD (n = 5).