Sinoatrial NodeSinoatrial BlockTachycardia, Sinoatrial Nodal ReentryLymph NodesAtrioventricular NodeBiological ClocksBradycardiaHeart AtriaHeart RateRabbitsAction PotentialsAtrial FunctionHeart Conduction SystemHyperpolarization-Activated Cyclic Nucleotide-Gated ChannelsArrhythmia, SinusModels, CardiovascularCyclic Nucleotide-Gated Cation ChannelsVagus NerveSick Sinus SyndromeAtrial Function, RightCalcium Channels, L-TypeElectrophysiologyHeart BlockMembrane PotentialsCalcium Channels, T-TypeConnexinsPotassium ChannelsTachycardia, SinusDogsHeartElectrocardiographyIsoproterenolIon ChannelsConnexin 43Cardiac Pacing, ArtificialPatch-Clamp TechniquesLymph Node ExcisionMyocytes, CardiacMyoblasts, CardiacMicroelectrodesAminophyllineDelayed Rectifier Potassium ChannelsAdrenergic beta-AgonistsGuinea PigsElectrophysiological PhenomenaBenzazepinesSentinel Lymph Node BiopsyCardiac MyosinsSodium ChannelsArrhythmias, CardiacRyanodinePacemaker, ArtificialCardiotonic AgentsAutonomic Nervous SystemAging, PrematureComputer SimulationAnti-Arrhythmia AgentsCalciumAcetylcholineSarcoplasmic ReticulumTachycardia, SupraventricularSodium-Calcium ExchangerCalcium SignalingNatriuretic Peptide, C-TypeParasympathetic Nervous SystemIon Channel GatingAtropineElectrophysiologic Techniques, CardiacRyanodine Receptor Calcium Release ChannelMyocardial ContractionTime FactorsLymphatic MetastasisPhosphodiesterase 3 Inhibitors