title: Properties of the fibers in the pathways along the anterior and posterior portions of the left A-V ring.
abstract: A comparison was made of the electrophysiological properties of the fibers between the previously reported conduction pathways from the left atrium to the right atrium and to the ventricle (left A-V ring pathways) and the ordinary atrial muscle, using perfused isolated rabbit hearts. Each fiber within these pathways showed action potential with a well-developed plateau phase. The plateau phase of these action potentials was distinctly shortened by an infusion of 1 x 10-6 g/ml of acetylcholine. When the heart was perfused by Tyrode solution with 15 mM KCl, the trans-membrane potential of the ordinary atrial muscle fiber showed a decrease of resting potential and of amplitude of action potential. The fibers within these pathways, however, were more resistant to the high potassium solution than the ordinary atrial fibers. A slow diastolic depolarization was observed in the fibers of the pathway when 1-isoproterenol (1 x 10-5 g/ml) was applied locally. These findings suggest that the fibers within the left A-B ring pathways possess similar electrophysiological properties to the specialized fibers in the atria.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000200:Action Potentials; D000818:Animals; D016275:Atrial Function; D004594:Electrophysiology; D006329:Heart Conduction System / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011690:Purkinje Fibers / Q000502:physiology; D011817:Rabbits; D016276:Ventricular Function
chemical_list: D007545:Isoproterenol; D000109:Acetylcholine; D011188:Potassium