FURA‐2 imaging of intracellular free Ca2+ dynamics and distribution induced by acetylcholine and caffeine in embryonic skeletal muscle cells

3 to 5 days‐old embryonic rat skeletal muscle cells (myotubes) present electrically‐induced [CA2+]ii transients uncoupled to any measurable contraction (quiescent myotubes). Acetylcholine (10−5 M) induces a transient variation of [Ca2+]i whose spatial maps, at the beginning of the oscillation, is similar to electrically and caffeine‐induced [Ca2+]i transients. Later (after 1 sec), the spatial distribution of [Ca2+]i is modified, suggesting a different mechanism undering the [Ca2+]i increase.