title: Differences in automaticity between Purkinje strands from right and left dog ventricle.
abstract: Previous in situ studies have implicated differences in the pacemaker rates between the left and right ventricular conduction system. Our studies were conducted to characterize automaticity in peripheral right and left canine Purkinje fibers in vitro. Standard microelectrode techniques were utilized. In paired right (RPF) and left (LPF) canine Purkinje fibers, control intrinsic rate (IR) was found to be higher in LPF (24.8 +/- 1.7 beats/min) than in RPF (11.5 +/- 1.5 beats/min, P less than 0.01). Following overdrive stimulation at various cycle lengths, LPF consistently showed earlier escape beats. In low K0+ (1.35 mM), IR increased comparably in both RPF and LPF. However, high K0+ (5.4 mM) resulted in a greater reducton of the IR in RPF (-78%) than in LPF (-58%). After epinephrine (10(-6) M) the IR of LPF > RPF although the chronotropic response was more pronounced in RPF. Adrenergic stimulation preceded by beta-adrenergic blockade did not produce significant differences in the intrinsic rate between RPF and LPF. These findings indicate that automaticity in right and left Purkinje strands is functionally dissimilar.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004285:Dogs; D004837:Epinephrine / Q000494:pharmacology; D006329:Heart Conduction System / Q000502:physiology*; D006352:Heart Ventricles / Q000294:innervation; D006706:Homeostasis; D066298:In Vitro Techniques; D009200:Myocardial Contraction; D011433:Propranolol / Q000494:pharmacology; D011690:Purkinje Fibers / Q000502:physiology*
chemical_list: D011433:Propranolol; D004837:Epinephrine