Autonomic nervous system mediates the cardiovascular effects of Rhodiola sacra radix in rats

• Published in: Journal of ethnopharmacology 2008-09, Vol.119 (2), p.284-290
• Main Authors: Shih, Cheng-Dean, Kuo, Daih-Huang, Huang, Chi-Wen, Gu, Yu-Hua, Chen, Fu-An
• Format: Article
• Language: English
• Subjects: animal models; Animals; antagonists; autonomic nervous system; Biological and medical sciences; blood pressure; Blood Pressure - drug effects; Cardiotonic Agents - administration & dosage; Cardiotonic Agents - pharmacology; cardiovascular agents; Crassulaceae; dosage; dose response; Dose-Response Relationship, Drug; fractionation; General pharmacology; heart rate; Heart Rate - drug effects; herbal medicines; Hypotension; Injections, Intravenous; Male; mechanism of action; Medical sciences; medicinal plants; medicinal properties; Medicine, Tibetan Traditional; muscle contraction; Myocardial Contraction - drug effects; myocardium; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; plant extracts; Plant Extracts - administration & dosage; Plant Extracts - pharmacology; Plant Roots; Rat; Rats; Rats, Sprague-Dawley; Renin-Angiotensin System - drug effects; Rhodiola; Rhodiola - chemistry; Rhodiola sacra; roots; Sympathetic vasomotor tone; Vagus Nerve - drug effects; Vagus Nerve - metabolism; Vasomotor System - drug effects; Vasomotor System - metabolism
• ISSN: 0378-8741; 1872-7573
• DOI: 10.1016/j.jep.2008.07.016

Rhodiola sacra (Crassulaceae) exhibits cardiovascular bioactivities and is used in Tibetan medicine for promoting circulation and preventing hypertension. However, the underlying mechanisms of its cardiovascular effects are poorly understood. The aim of this study was therefore to evaluate the cardiovascular activity of water-soluble fraction (WtF) and n-butanol-soluble fraction (BtF) of Rhodiola sacra radix and to explore its mechanism of action in propofol anesthetized Sprague–Dawley rats. The changes of blood pressure, heart rate and cardiac contractility after systemic administration of the extracts (10–75 mg/kg) were examined for at least 40 min. Different antagonists were used to evaluate the mechanisms of cardiovascular effects of the extracts. Intravenous injection of the WtF (10, 25, 35, 50 or 75 mg/kg) exhibited dose-dependent hypotension and increases in heart rate and cardiac contractility. In contrast, mild alterations in the same cardiovascular parameters were detected only at high dose (75 mg/kg) BtF. The WtF-induced hypotensive, positive inotropic and chronotropic effects were significantly abolished by pretreatment with hexamethonium (30 mg/kg, i.v.) or reserpine (5 mg/kg, i.v.), whereas the hypotensive, but not the positive inotropic or chronotropic effect was potentiated by captopril (2.5 mg/kg, i.v.). Pretreatment with methylatropine (1 mg/kg, i.v.), on the other hand, reversed the positive inotropic and chronotropic but not the hypotensive effects of WtF. The WtF-induced cardiovascular responses were not affected in rats pretreated with N G-nitro- l-arginine methyl ester (20 mg/kg, i.v.). We conclude that systemic administration of the WtF of Rhodiola sacra radix elicited a potent hypotensive effect that was mediated by the withdrawal of sympathetic vasomotor tone and interaction with the circulatory angiotensin system. The positive inotropic and chronotropic effects of WtF may result from a direct vagal inhibition on the heart.