Sinoatrial NodeCaffeineSinoatrial 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 SyndromeMembrane PotentialsElectrophysiologyAtrial Function, RightCalcium Channels, L-TypeHeart BlockHeartPotassium ChannelsDogsCalcium Channels, T-TypeConnexinsRyanodineTachycardia, SinusIsoproterenolIon ChannelsElectrocardiographyConnexin 43Patch-Clamp TechniquesCalciumMyocytes, CardiacCardiac Pacing, ArtificialLymph Node ExcisionSarcoplasmic ReticulumMyoblasts, CardiacMicroelectrodesCentral Nervous System StimulantsGuinea PigsAminophyllineAdrenergic beta-AgonistsDelayed Rectifier Potassium ChannelsRyanodine Receptor Calcium Release ChannelElectrophysiological PhenomenaBenzazepinesSentinel Lymph Node BiopsyTheobromineCardiac MyosinsArrhythmias, CardiacAcetylcholineCardiotonic AgentsCalcium SignalingPacemaker, ArtificialSodium ChannelsAutonomic Nervous SystemCoffeeAging, PrematureAnti-Arrhythmia AgentsComputer SimulationTachycardia, SupraventricularSodium-Calcium ExchangerParasympathetic Nervous SystemNatriuretic Peptide, C-TypeMyocardial ContractionIon Channel GatingCalcium ChannelsTime FactorsAtropineElectrophysiologic Techniques, CardiacLymphatic MetastasisPhosphodiesterase 3 InhibitorsPapillary Muscles