Whole-cell recording techniques were used on single right atrial myocytes to study the ionic currents that may be responsible for the diverse diastolic voltage characteristics of atrial tissue. Ionic currents were activated by hyperpolarizing voltage pulses negative to -30 mV. In general, four different types of cells were identified based primarily on the ionic currents elicited during hyperpo...

Abstract Introduction Ivabradine is a selective inhibitor of sodium’s If current; it acts at the level sinus node causing bradycardizing effect without on inotropism and atrioventricular conduction. In fact, channel, located in pacemaker cells, activated hyperpolarization allows membrane potential to become gradually more positive until threshold reached. Previous studies have actually shown us...

The sino-atrial node area was perfused selectively through the right atrial artery in 76 dogs. The relationship between changes in the blood pressure in this artery and sinus node rhythmicity was studied in 56 hearts in which the major blood supply to the sinus node artery came from the right atrial artery. A reciprocal relation was observed between changes of blood pressure in the sinus node a...

Atrial fibrillation (AF) is a significant contributor to cardiovascular morbidity and mortality. The currently available treatments are limited and AF continues to be a major clinical challenge. Clinical studies have shown that AF is frequently associated with dysfunction in the sino-atrial node (SAN). The association between AF and SAN dysfunction is probably related to the communication betwe...

• Cardiac arrest, produced by an increased extracellular potassium concentration, was first observed by Ilering in 1907. Recent studies with microelectrodes have revealed that an increased potassium concentration decreases the transmembrane potential of fibers of atrium,' ventricle' and the Purkinje system. Sensitivity to potassium, however, differs for the several tissues. Conduction fails ear...

The perfusion of the sinus node artery in dogs in situ was performed. The selective administration of nicotine and DMPP into the sinus node artery induced a biphasic response, i.e., a negative chronotropic response followed by a positive one. Both compounds produced similar negative chronotropic responses, but positive responses were more markedly induced by DMPP than by nicotine. These negativ...