IsoproterenolMyocytes, CardiacAdrenergic beta-AgonistsReceptors, Adrenergic, betaMyocardiumHeart VentriclesMyocardial ContractionCalciumCyclic AMPCells, CulturedPropranololMuscle CellsColforsinVentricular FunctionCalcium Channels, L-TypeAdenylate CyclaseGuinea PigsSympathomimeticsHeartReceptors, AdrenergicReceptors, Adrenergic, beta-1Receptors, Adrenergic, beta-2Cardiotonic AgentsSarcoplasmic ReticulumPatch-Clamp TechniquesRats, Sprague-DawleyCardiomegalyHeart AtriaAdrenergic beta-AntagonistsSodium-Calcium ExchangerAction PotentialsPhenylephrineCyclic AMP-Dependent Protein KinasesRats, WistarDogsMembrane PotentialsCalcium SignalingParotid GlandDihydroalprenololPropanolaminesPotassium ChannelsIodocyanopindololAdrenergic AgonistsNorepinephrineSarcolemmaBucladesinePindololAnimals, NewbornDose-Response Relationship, DrugRabbitsEpinephrineAdrenergic alpha-AgonistsElectrophysiology8-Bromo Cyclic Adenosine MonophosphateCatecholaminesStimulation, ChemicalCalcium ChannelsAlprenolol1-Methyl-3-isobutylxanthineKineticsCaffeineAdrenergic beta-1 Receptor AgonistsCell SizeSarcoplasmic Reticulum Calcium-Transporting ATPasesRyanodine Receptor Calcium Release ChannelTime FactorsGTP-Binding Protein alpha Subunits, GsHeart RatePapillary MusclesCarbacholPhosphorylationSignal TransductionElectric ConductivityEnzyme InhibitorsArrhythmias, CardiacExcitation Contraction CouplingAtrial FunctionPotassiumReceptors, Adrenergic, alphaPhosphodiesterase InhibitorsAdenosineRats, Inbred StrainsSarcomeresRNA, MessengerReceptors, Adrenergic, beta-3SodiumCalcium-Binding ProteinsAnti-Arrhythmia AgentsElectric StimulationDelayed Rectifier Potassium ChannelsCalcium Channel BlockersCell SeparationCalcium-Transporting ATPasesCalcium Channel AgonistsAdrenergic beta-1 Receptor AntagonistsModels, CardiovascularRyanodineEnzyme ActivationHeart FailureGTP-Binding Proteins