Spatiotemporal characteristics of spontaneous Ca2+ sparks are different in mouse RPASMCs, CPASMCs and MASMCs. a Original line scan images show spontaneous Ca2+ sparks recorded in an RPASMC and MASMC. b Graphs summarize spatiotemporal characteristics of spontaneous Ca2+ sparks in RPASMCs (44 sparks, 31 cells), CPASMCs (84 sparks, 28 cells) and MASMCs (35 sparks, 12 cells). * p < 0.05 compared with RPASMCs; + p < 0.05 compared with CPASMCs.