Sinoatrial NodeSinoatrial BlockTachycardia, Sinoatrial Nodal ReentryLymph NodesAtrioventricular NodeBiological ClocksBradycardiaGap JunctionsHeart AtriaIntercellular JunctionsTight JunctionsHeart RateRabbitsAction PotentialsAtrial FunctionHeart Conduction SystemHyperpolarization-Activated Cyclic Nucleotide-Gated ChannelsConnexinsArrhythmia, SinusModels, CardiovascularConnexin 43Cyclic Nucleotide-Gated Cation ChannelsVagus NerveAdherens JunctionsSick Sinus SyndromeNeuromuscular JunctionElectrophysiologyDogsMembrane PotentialsAtrial Function, RightCalcium Channels, L-TypeHeart BlockCalcium Channels, T-TypeHeartPotassium ChannelsIon ChannelsTachycardia, SinusElectrocardiographyIsoproterenolPatch-Clamp TechniquesMyocytes, CardiacCardiac Pacing, ArtificialLymph Node ExcisionMicroelectrodesMyoblasts, CardiacAminophyllineGuinea PigsDelayed Rectifier Potassium ChannelsAdrenergic beta-AgonistsElectrophysiological PhenomenaBenzazepinesSentinel Lymph Node BiopsyCardiac MyosinsArrhythmias, CardiacAcetylcholineCalciumSodium ChannelsPacemaker, ArtificialRyanodineAutonomic Nervous SystemCardiotonic AgentsComputer SimulationAnti-Arrhythmia AgentsAging, PrematureSarcoplasmic ReticulumTachycardia, SupraventricularCalcium SignalingSodium-Calcium ExchangerParasympathetic Nervous SystemNatriuretic Peptide, C-TypeIon Channel GatingAtropineElectrophysiologic Techniques, CardiacTime FactorsRyanodine Receptor Calcium Release ChannelMyocardial ContractionMice, KnockoutLymphatic MetastasisImmunohistochemistryPhosphodiesterase 3 Inhibitors