Chronotropic and Inotropic effects of Passiflora Foetida extracts on rat isolated atria

Abstract

Passiflora foetida is a Thai herbal plant. It has been reported that P. foetida extract possessed potential antidepressant actions in the in vivo model of depression, mice swimming test. Although the mechanisms of actions were not yet known, the receptor binding studies reveled that P. foetida extracts were able to bind to dopamine and serotonin receptors. This study aims to investigate the mechanisms of inotropic and chronotropic effects produced by P. foetida extracts, using the model of isolated rat atria (250 – 300 g). The results showed that P.foetida extracts, subfraction PF003-2 (100 µg/ml) had transiently depressed contractile force on both left and right atria, followed by significant increasing the force of contraction by 8.76±4.01% and 19.22 ± 4.95 % at 3min and 15 min, respectively (p<0.05, n=6). PF003-2 had no significant chronotropic effect on right atria. PF003-(3-5), by contrast, showed significant negative chronotropic effect to right atria by 9.61 ±1.53 and 14.87±1.17 % (p<0.05) in 3 min and 15 min. The positive inotropic effect of PF003-2 was significantly partially inhibited by propranolol (10 µM) and ketanserin (10 µM) and was completely inhibited by pretreatment of propranolol(10 µM) and ketanserin (10 µM) together (p<0.05, n=5). PF003-2 possessed intrinsic inotropic activity which did not relate to Ca2+ release from SR and inhibition effect to reuptake of NE and serotonin In conclusion, the results in this study suggested that each of PF extracts were different in their inotropic and chronotropic action on the isolated rat atria. It has been suggested that PF003-(3-5) had potential effects on pace maker activity. Positive inotropic effect of PF003-2 was not related to a release of Ca2+from SR and an inhibition of NE and serotonin reuptake. It is possible that PF003-2 may have biphasic activity on isolated rat atria. In addition, PF003-2 may exerted its positive inotropic effect via activation on β-adrenoceptor and serotonin receptor.