HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Earm, Y E Articles by Spindler, A J Search for Related Content PubMed PubMed Citation Articles by Earm, Y E Articles by Spindler, A J

A modified single-sucrose-gap system was used to study sheep atrial trabeculae under voltage-clamp conditions. A time- and voltage-dependent current system is described, which resembles the current if in Purkinje fibres. This current was activated at membrane potentials of between -60 and -70 mV in many fibres. The addition of Ba2+ reduced the instantaneous current (the 'jump') and thus facilitated the study of the current if. Current tails were more prominent in the presence of TTX and Mn2+. Most experiments were done in the presence of Ba2+, Mn2+ and TTX. Standard envelope tests and conductance measurements indicated that this current is an inward current, activated on hyperpolarization. We have also labelled the atrial current if. The instantaneous fully activated current-voltage relationship, i(E) was found to be linear in the activation range. Increasing the level of K+, which increased the current magnitude, also increased the slope of the i(E) curve. The current magnitude was also dependent on the level of Na+ in the medium. The current magnitude was increased by adrenaline or isoprenaline. Only a small part of the increase could be attributed to a shift in the voltage dependence of the gating kinetics. The shifts in activation curves were much smaller (3-4 mV in the depolarizing direction) than those in Purkinje fibres. Large shifts in activation curves were obtained with theophylline, indicating that the presence of Ba2+ or Mn2+ did not occlude any shifts by adrenaline. The magnitude of if was increased by theophylline, with a further increase by adrenaline. There is therefore no mutual occlusion of the two effects on if. The slope of the i(E) curve was increased by isoprenaline, indicating that there was an increase in conductance. The presence of propranolol did not prevent the increase in current amplitude by isoprenaline. A direct effect of catecholamines on the channel is suggested.

This article has been cited by other articles:

				E. Carmeliet Cardiac Ionic Currents and Acute Ischemia: From Channels to Arrhythmias Physiol Rev, July 1, 1999; 79(3): 917 - 1017. [Abstract] [Full Text] [PDF]

				U. C Hoppe and D. J Beuckelmann Characterization of the hyperpolarization-activated inward current in isolated human atrial myocytes Cardiovasc Res, June 1, 1998; 38(3): 788 - 801. [Abstract] [Full Text] [PDF]

				U. C. Hoppe, E. Jansen, M. Sudkamp, and D. J. Beuckelmann Hyperpolarization-Activated Inward Current in Ventricular Myocytes From Normal and Failing Human Hearts Circulation, January 13, 1998; 97(1): 55 - 65. [Abstract] [Full Text] [PDF]

				A. Moroni, L. Gorza, M. Beltrame, B. Gravante, T. Vaccari, M. E. Bianchi, C. Altomare, R. Longhi, C. Heurteaux, M. Vitadello, et al. Hyperpolarization-activated Cyclic Nucleotide-gated Channel 1 Is a Molecular Determinant of the Cardiac Pacemaker Current If J. Biol. Chem., July 27, 2001; 276(31): 29233 - 29241. [Abstract] [Full Text] [PDF]