Fig. 6.

A–E. Spontaneous and nerve-evoked fast Ca²⁺ transients. A shows a FOV from which an ST map was constructed by averaging Ca²⁺ intensities in myofibers parallel to their long axis (see dashed rectangle). B shows the pattern of fast Ca²⁺ transients over time in ~15 active myofibers. Note the variable intensity and interval of fast Ca²⁺ transients both within individual myofibers (a single horizontal row) and between multiple myofibers (multiple rows). C shows a FOV in an experiment in which four pulses of electrical nerve stimulation were applied (~ every 5–8 s). Note the synchronous activation of many myofibers in the ST map shown in D. The frequency histogram of half-maximal duration shows a bi-phasic distribution (E; black bars) with two peaks located at ~75 ms and ~110 ms and a trough at ~90 ms. Faster events (<90 ms) were described as Type-1, and slower events (>90 ms) as Type-2 fast Ca²⁺ transients. Nerve-evoked fast Ca²⁺ transients were predominantly Type-1 (<90 ms). Histogram data were compiled from 350 transients examined in seven EOMs.