Figure 2.

CEPN blocks high K⁺-evoked Ca²⁺ influx. (a) A representative tracing of 4 experiments. Under Ca²⁺-free conditions (0 Ca²⁺ and 0.5 mM EGTA), high K⁺ did not evoke contraction in a tracheal ring. After the restoration of 2 mM Ca²⁺, a sustained contraction occurred, which was fully inhibited by CEPN. (b) In the presence of 1 mg/mL CEPN, the identical experiments as above were performed. A Ca²⁺ restoration-provoked contraction was not noted. This experiment was conducted in 6 tracheal rings. These results suggest that CEPN inhibits Ca²⁺ influx.