Objective: To investigate the effect of aqueous extract of Polygala tenuifolia(APT) on myocardial contractility and atrial natriuretic peptide (ANP) secretion in beating rabbit atria. Method: The APT-induced changes in atrial dynamics

cAMP efflux and ANP secretion were determined in perfused beating rabbit atria. The changes of cAMP and ANP were measured by radioimmunoassay. Result: APT increased atrial stroke volume

pulse pressure and cAMP efflux in a concentration-dependent manner with inhibition of ANP secretion in beating rabbit atria. The APT-induced positive inotropic effect was significantly blocked by pretreatment with blockade of β and β1-adrenoceptors (AR) (P<0.05) but not β2-AR. Furthermore

the APT-induced changes in myocardial contractility were attenuated by inhibition of L-type Ca2+channel and protein kinase A(PKA) activation with no changes in cAMP efflux. Conclusion: APT could increase atrial dynamics via β1-AR-cAMP-Ca2+signaling and decreases ANP secretion in beating rabbit atria.