Spark- and ember-like elementary Ca2+ release events in skinned fibres of adult mammalian skeletal muscle

1. Using laser scanning confocal microscopy, we show for the first time ele mentary Ca2+ release events (ECRE) from the sarcoplasmic reticulum in chemi cally and mechanically skinned fibres from adult mammalian muscle and compa re them with ECRE from amphibian skinned fibres. 2. Hundreds of spontaneously occurring events could be measured from indivi dual single skinned mammalian fibres. In addition to spark-like events, we found ember-like events, i.e. long-lasting events of steady amplitude. Thes e two different fundamental release types in mammalian skeletal muscle coul d occur in combination at the same location. 3. The two peaks of the frequency of occurrence for ECRE of mammalian skele tal muscle coincided with the expected locations of the transverse tubular system within the sarcomere, suggesting that ECRE mainly originate at triad ic junctions. 4. ECRE in adult mammalian muscle could also be identified at the onset of the global Ca2+ release evoked by membrane depolarisation in mechanically s kinned fibres, In addition, the frequency of ECRE was significantly increas ed by application of 0.5 nim caffeine and reduced by application of 2 nim t etracaine. 5. We conclude that the excitation-contraction coupling process in adult ma mmalian muscle involves the activation of both spark- and ember-like elemen tary Ca2+ release events.