The Effects of Piperine on Isolated Right and Left Rat Atria

Abstract

The effects of piperine on cardiovascular system have been studied on isolated right and left rat atria. Piperine at five doses,3, 6,12,24, and 48μg/ml, was found to produce dose-dependent positive chronotropy and inotropy on isolated right and left rat atria respectively. The time to maximum effect on both right atrial rate and left atrial isometric tension were about 3-5 min after addition of drug. With high doses (24 and 48 μg/ml) these initial stimulations were followed by depression of both the rate and contractile force. Reserpine pretreatment greatly reduced the positive chronotropy and inotropy about 58% and 98% respectively. In addition, the positive chronotropic effect of piperine was attenuated by 0.15μg/ml propranolol (about 50%). Alpha-adrenoceptor blocking agent (phentolamine 0.32μg/ml) and 5-HT antagonist (methylsergide 0.47μg/ml and cyproheptadine 0.02μg/ml) did not affect both positive chronotropy and inotropy. Neuronal uptake inhibitor of noradrenaline, desipramine 0.27μg/ml and cocaine 9.1μg/ml, greatly reduced the positive chronotropic and inotropic effects by 60% and 90% respectively. It is concluded that piperine mediates the positive chronotropic and inotropic effects mainly by indirectly stimulates the release of catecholamine from adrenergic nerve in atria.