Heart AtriaMyocytes, CardiacAtrial FunctionMyocardiumPotassium ChannelsMuscle CellsPatch-Clamp TechniquesCalcium Channels, L-TypeHeartHeart VentriclesCalciumAction PotentialsG Protein-Coupled Inwardly-Rectifying Potassium ChannelsKv1.5 Potassium ChannelGuinea PigsCells, CulturedDelayed Rectifier Potassium ChannelsMembrane PotentialsMyocardial ContractionSarcoplasmic ReticulumCalcium SignalingElectrophysiologyIsoproterenolPotassium Channels, Voltage-GatedReceptors, MuscarinicCalcium ChannelsSarcolemmaAtrial Natriuretic FactorPotassium Channel BlockersAdrenergic beta-AgonistsExcitation Contraction CouplingAcetylcholineVentricular FunctionSodium-Calcium ExchangerCaffeineRana catesbeianaPotassiumElectric ConductivityAtrial FibrillationAtrial AppendageShal Potassium ChannelsPotassium Channels, Inwardly RectifyingCatsRyanodine Receptor Calcium Release ChannelMicroscopy, ConfocalParasympathetic Fibers, PostganglionicAnti-Arrhythmia Agents4-AminopyridineRats, Sprague-DawleyCell SizeIon TransportArrhythmias, CardiacReceptor, Muscarinic M2Receptors, Adrenergic, betaIon Channel GatingSodium ChannelsReceptors, Serotonin, 5-HT4AminobenzoatesCytophotometryRyanodineAcetanilidesRabbitsRats, WistarCell SeparationRefractory Period, ElectrophysiologicalDisopyramideModels, CardiovascularDogsBee VenomsKineticsPhenylephrineCalcium Channel BlockersDose-Response Relationship, DrugPhosphatidylinositol 4,5-DiphosphatePotassium Channels, Tandem Pore DomainElectric StimulationCardiotonic AgentsEndothelin-1Ion ChannelsTime FactorsAdrenergic alpha-AgonistsSignal TransductionCholinergic AgentsQuinidineSulfonamidesSodiumLanthanoid Series ElementsInositol 1,4,5-Trisphosphate ReceptorsAdenosine TriphosphateAdenosineSodium Channel BlockersHeart Conduction SystemPertussis ToxinReceptors, Purinergic P1Cyclic AMP-Dependent Protein KinasesSinoatrial NodeCyclic AMPGTP-Binding ProteinsStimulation, ChemicalMuscarinic Agonists