Cardiotonic activity of the rhizome of Polygonatum sibiricum in rats

The cardiotonic effect of the rhizome of Polygonatum sibiricum was investigated in the left atria of rats. The methanol extract of the rhizome of Polygonatum sibiricum (OM) (1-7 mg/ml) concentration-dependently increased the developed tension of the left atrium. It also strongly inhibited cAMP phosphodiesterase. The increase cAMP level correlated the increase in left atrial contraction. On the other hand, OM did not inhibit Na+, K+-ATPase. The cardiotonic effect of OM was strongly inhibited by reserpine, a sympatholytic agent. Furthermore, OM-treated left atria inhibited the tension produced by propranolol, a beta adrenocepter antagonist. These findings suggested that the cardiotonic effect is due to stimulating beta adrenoceptors through activation of sympathetic nerves.