Figure 1.

Self-sustained repetitive activity and its modulation by ryanodine and caffeine in isolated atrial myocytes from Casq2^−/− mice

A, confocal Ca line scan showing self-sustained repetitive activity in a Casq2^−/− atrial myocyte. Diastolic Ca releases (DCR), triggered activity (TA) and self-sustained repetitive activity are marked by pink arrows and traces. Pacing is indicated by black line markers. B, simultaneous membrane potential (MP) and intracellular Ca recordings in a Casq2^−/− atrial myocyte. A slow phase of Ca release represents DCR and is associated with delayed afterdepolarization (DAD), and a rapid phase of Ca releases (marked by a downward black arrow) represents systolic Ca release and is exclusively linked to action potential (AP). C, the percentage of hearts (WT, n = 10; Casq2^−/−, n = 25) that have self-sustained repetitive activity in isolated atrial myocytes indicated as inducibility, together with the duration of repetitive activity. D, representative Ca recordings before and after the application of ryanodine (3 μm) in Casq2^−/− atrial myocytes (n = 5). E, the duration of self-sustained repetitive activity before and after the application of ryanodine (Rya). F, representative Ca recordings before and after the application of 0.2–0.5 mm caffeine in WT atrial myocytes (n = 6). G, the duration of self-sustained repetitive activity before and after the application of caffeine (Caf). Isoproterenol (100 nm) was present in all conditions (A–G).