Myocytes, CardiacMyocardiumHeart VentriclesMuscle CellsMyocardial ContractionHeartCalciumCells, CulturedVentricular FunctionCalcium Channels, L-TypePatch-Clamp TechniquesSodium-Calcium ExchangerGuinea PigsSarcoplasmic ReticulumIsoproterenolHeart AtriaAction PotentialsPotassium ChannelsMembrane PotentialsCalcium SignalingRats, Sprague-DawleyAnimals, NewbornSarcolemmaCardiomegalyAdrenergic beta-AgonistsCell SizeCaffeineCalcium ChannelsElectrophysiologyRats, WistarSarcoplasmic Reticulum Calcium-Transporting ATPasesRyanodine Receptor Calcium Release ChannelRabbitsReceptors, Adrenergic, betaSarcomeresElectric ConductivityExcitation Contraction CouplingCell SeparationModels, CardiovascularSodium ChannelsDelayed Rectifier Potassium ChannelsSodiumMitochondria, HeartCardiotonic AgentsIon Channel GatingPotassium Channels, Voltage-GatedMicroscopy, ConfocalPotassiumAtrial FunctionMuscle Fibers, SkeletalCalcium-Transporting ATPasesReceptors, Adrenergic, beta-1CalsequestrinCalcium Channel BlockersTime FactorsDogsMuscle ProteinsSignal TransductionEnzyme InhibitorsAnti-Arrhythmia AgentsDose-Response Relationship, DrugEndocardiumIon TransportRyanodineArrhythmias, CardiacPericardiumPotassium Channel BlockersPhenylephrineCyclic AMP-Dependent Protein KinasesProtein Kinase CEndothelin-1Calcium Channel AgonistsShal Potassium ChannelsBenzophenanthridinesElectric StimulationRNA, MessengerAtrial Natriuretic FactorIon Channels4-AminopyridineKineticsSodium-Potassium-Exchanging ATPaseKv1.5 Potassium ChannelCaveolin 3Heart FailureFluorescent DyesConnexin 43PhosphorylationCyclic AMPAdenosine TriphosphateMyocardial Reperfusion InjuryMyosin Heavy ChainsCardiomyopathiesMyofibrilsReceptors, Adrenergic, alpha-1Intracellular FluidMice, TransgenicReceptors, Adrenergic, beta-2PhenanthridinesPhosphodiesterase InhibitorsDiacetyl