Figure 5.

K⁺ induced depolarization increased the frequency of Ca²⁺ sparks. (A) Original recordings of Ca²⁺ sparks in the absence (top trace), presence (middle trace) and washout (bottom trace) of 37.5 mM K⁺. Numbers beside transients indicate sparks. (B) Elevation of extracellular K⁺ from 3.6 to 37.5 mM increased the frequency of Ca²⁺ sparks but had no effect on amplitude, rise and half decay times of Ca²⁺ sparks. Recordings in the presence of 37.5 mM K⁺ were made at 10, 40 and 70s after K⁺ application and recordings during washout were made at 10, 40 and 70s after termination of K⁺ application. Time control experiments are replotted from Figure 3.