Stretch-mediated interaction between the auricle and ventricle in an oyster Crassostrea gigas

1. 1. Mediating factors of co-ordination of rhythms between the auricle and ventricle and the effect of a brief stretch on the electrical activity of the myocardium were studied in the heart of oyster. 2. 2. The co-ordination was maintained even in the state where only mutual stretching between the auricle and ventricle was kept and no electrical connection was found between them. Thus it was assumed that the co-ordination is mediated by mutual stretching without direct interactions in their electrical activities. 3. 3. A brief stretch altered the periodic membrane potential changes of the myocardium and caused prolongation or shortening of the beat interval depending on the moment of its application. 4. 4. Mechanism of the co-ordination of rhythms mediated by mutual stretching between the auricle and ventricle was discussed in relation to the positive and negative chronotropic effects on the beat interval by the brief stretch.