ฤทธิ์ของไปเปอรีนที่มีต่อความดันโลหิตและหัวใจห้องบนขวา และซ้ายที่แยกจากหนูขาว

Abstract

The effects of piperine on cardiovascular system have been studied in anesthetized rats and on isolated right and left rat atria. Intravenous administration of 1 mg/kg piperine in anesthetized rats produced an initial brief fall in blood pressure, bradycardia and apnea, followed by a rise in tension and by a subsequent delayed fall in blood pressure. The Bezold-Jarisch reflex (hypotension, bradycardia and apnea) was completely abolished by bilateral vagotomy. The rise in blood pressure, which followed the triad response, was partially reduced by 5 mg/kg hexamethonium (about 57%). The combination of 0.07 mg/kg propranolol and 1 mg/kg phentolamine could lessen the pressor effect by 65%. Furthermore, intravenous injection of 1 mg/kg piperine could also produce a sharp rise in blood pressure in pithed rat. Phentolamine, propranolol as well as reserpinbe pretreatment greatly reduced this pressor effect of piperine. In isolated right and left atria, piperine at five doses, 3,6,12,24 and 48 ug/ml, was found tio produce a dose-dependent positive chronotropy and inotropy respectively. The time to maximum effect on both right atrial rate and left artial isometric tension were about 3-5 min after the addition of drug. With high dosed (24 and 48 ug/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 90% respectively. In addition, the positive chronotropic effect of piperine was attenuated by 0.15 ug/ml propranolol (abiy 50%). Alpha-adrenoceptor blocking agent (phentolamine 0.32 ug/ml) and 5-HT antagonist (methysergide 0.47 ug/ml and cyproheptadine 0.02 ug/ml) did not affect both positive chrobnotropy and inotropy. Neuronal uptake inhibitor of noradrenaline, desipramine 0.27 ug/ml and cocaine 9.1 ug/ml, greatly reduced the positive chronotropic and inotropic effects by 60% and 90% respectively. It is concluded that a) piperine induces the Bezold-Jarisch reflex mediated by the afferent fiber of vagus nerve. The rise in blood pressure after the triad response may be due to central activation of sympathetic system as well as peripheral mechanism which apparently involves the release of catecholamine; and b) piperine indirectly mediates the positive chronoropic and inotropic effects on isolated atria mainly by stimulates the release of catecholamine from adrenergic nerve in the atria.