[Automatic activity of pacemaker cells in the atrioventricular valves of the rabbit heart]

The microelectrode technique applied revealed an automatic activity of the pacemaker cells with slow diastolic depolarization in the cusps of the atrioventricular valves obtained from 34 rabbit hearts. Electrophysiological characteristics of the action potentials of these cells were investigated. Inhibitors of slow sodium-calcium canal (Mn++, Co++, and Mg++ ions) proved to eliminate the automatic activity of the pacemaker cells. When the content of potassium ions was elevated in the perfusion solution, no suppression occurred. It is suggested that the automatic activity of the pacemaker cells in the atrioventricular values depended mainly on the functioning of the slow sodium-calcium canal.